Sujata Sharma

• Professor
• Professor at All India Institute of Medical Sciences

The emergence of multidrug-resistant Acinetobacter baumannii poses a significant challenge in healthcare settings, highlighting the urgent need for new therapeutic strategies. This study investigates the inhibition potential of four natural compounds, epicatechin, quercetagetin, myricetin, and morin, against histidinol-phosphate aminotransferase (H...

Lactoperoxidase (LPO) is a heme‐containing mammalian enzyme that is found in the extracellular fluids of animals including plasma, saliva, airway epithelial and nasal lining fluids, milk, tears, and gastric juices. LPO uses hydrogen peroxide (H 2 O 2 ) to convert substrates into oxidized products. Previous structural studies have shown that H 2 O 2...

Aim: Currently, we have limited armamentarium of antifungal agents against Mucorales. There is an urgent need to discover novel antifungal agents that are effective, safe and affordable. Materials & methods: In this study, the anti-Mucorale action of native lactoferrin (LF) and its functional fragments CLF, RR6 and LFcin against three common Mucora...

Mucormycosis, a rare but deadly fungal infection, was an epidemic during the COVID-19 pandemic. The rise in cases (COVID-19-associated mucormycosis, CAM) is attributed to excessive steroid and antibiotic use, poor hospital hygiene, and crowded settings. Major contributing factors include diabetes and weakened immune systems. The main manifesting fo...

Phosphopantetheine adenylyltransferase (EC. 2.7.7.3, PPAT) catalyzes the penultimate step of the multistep reaction in the coenzyme A (CoA) biosynthesis pathway. In this step, an adenylyl group from adenosine triphosphate (ATP) is transferred to 4′-phosphopantetheine (PNS) yielding 3′-dephospho-coenzyme A (dpCoA) and pyrophosphate (PPi). PPAT from...

Lactoperoxidase (LPO) is a heme containing mammalian enzyme which uses hydrogen peroxide (H2O2) to catalyze the conversion of substrates into oxidized products. LPO is found in body fluids and tissues such as milk, saliva, tears, mucosa and other body secretions. The previous structural studies have shown that LPO converts substrates, thiocyanate (...

Mucormycosis is a fungal infection of the sinuses, brain and lungs that is the cause of approximately 50% mortality rate despite the available first-line therapy. Glucose-Regulated Protein 78 (GRP78) is already reported to be a novel host receptor that mediates invasion and damage of human endothelial cells by Rhizopus oryzae and Rhizopus delemar,...

We draw the attention of readers and governments to the death rate from coronavirus disease 2019 in Japan, continuing as a fraction of that experienced by many other developed nations. We think this is due to the activity of the powerful, protective lactoperoxidase system (LPO) which prevents serious airborne infections. The LPO system requires iod...

Lactoperoxidase (LPO, E.C. 1.11.1.7) is a heme containing enzyme of the innate immune system which uses hydrogen peroxide (H 2 O 2 ) to catalyze the conversion of substrates into antimicrobial products. It is found in the body extracellular fluids including plasma, saliva, airway epithelial lining fluids, nasal lining fluid, milk, tears and gastric...

Lactoperoxidase (LPO) is a glycosylated antimicrobial protein present in milk with a molecular mass of 78 kDa. LPO is included in many biological processes and is well-known to have biocidal actions, acting as an active antibiotic and antiviral agent. The wide spectrum biocidal activity of LPO is mediated via a definite inhibitory system named lact...

The short peptidoglycan recognition protein (PGRP-S) of the innate immune system recognizes the invading microbes through binding to their cell wall molecules. In order to understand the mode of binding of PGRP-S to bacterial cell wall molecules, the structure of the complex of camel PGRP-S (CPGRP-S) with hexanoic acid has been determined at 2.07 Å...

Peptidoglycan recognition proteins (PGRPs) are important components of the innate immune system which provide the first line of defense against invading microbes. There are four members in the family of PGRPs in animals of which PGRP-S is a common domain. It is responsible for the binding to microbial cell wall molecules. In order to understand the...

Background The ESKAPE group of pathogens which comprise of multidrug resistant bacteria, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species are the cause of deadly nosocomial infections all over the world. While these pathogens have developed robust st...

Lactoferrin (LF) is an iron-binding glycoprotein released from mucous secreting cells and neutrophils. LF can be used in a broad range of eye diseases related to the retina, cornea, and optic nerve. The retina is particularly affected by oxidative stress inside the photoreceptor being constantly exposed to light which induces accumulation of reacti...

Proteins are flexible biomolecules and can adopt a wide range of structural conformations such that they can have their whole conformational ensemble. Understanding of protein function is not complete without proper knowledge of protein dynamics. The nature of these structural transitions, their probabilities, and the time span for each conformatio...

The presentation describes the ternary complex of lactoperoxidase with hydrogen peroxide and iodide ions. It also describes the stability of hydrogen peroxide in the active site region of lactoperoxidase.

Lactoperoxidase (1.11.1.7, LPO) is a mammalian heme peroxidase found in the extracellular fluids of mammals including plasma, saliva, airway epithelial lining fluids, nasal lining fluid, milk, tears, gastric juices, and intestinal mucosa. To perform its innate immune action against invading microbes, LPO utilizes hydrogen peroxide (H2O2) to convert...

Structural evidence of the oxidation of iodide ion into hyper-reactive hypoiodite ion by mammalian heme lactoperoxidase

C-lobe represents the C-terminal half of lactoferrin which is a bilobal 80 kDa iron binding glycoprotein. The two lobes are designated as N-lobe (Ser1-Glu333) and C-lobe (Arg344-Arg689). The N- and C-lobes are connected by a 10-residue long α-helical peptide (Thr334-Thr343). Both lobes adopt similar conformations and have identical iron binding sit...

The mammalian lactoperoxidase system, consisting of lactoperoxidase and the H2 O2 -producing enzyme duox, is our first line of defence against airborne microbes. This system catalyses the production of hypoiodite and hypoiodous acid in the presence of sufficient iodine. These products are highly efficient at destroying the H1N1 virus and the respir...

Acinetobacter baumannii is an extremely dangerous multidrug-resistant (MDR) gram-negative pathogen which poses a serious life-threatening risk in immunocompromised patients. Phosphopantothenoyl cysteine synthetase (PPCS) catalyzes the formation of an amide bond between L-cysteine and phosphopantothenic acid (PPA) to form 4′- Phosphopantothenoylcyst...

The Peptide bond between Arg341▬Tyr342 in the bilobal lactoferrin (Ala1-Arg689) acts as a cleavage site for serine proteases to generate the perfect C-lobe (Tyr342-Arg689): Structure of the pepsin hydrolyzed lactoferrin C-lobe at 2.28 Å resolution

Lactoperoxidase (LPO) is a mammalian heme peroxidase which catalyzes the conversion of thiocyanate (SCN‾) and iodide (I −) by hydrogen peroxide (H 2 O 2) into antimicrobial hypothiocyanite (OSCN‾) and hypoiodite (IO −). The prosthetic heme group is covalently attached to LPO through two ester linkages involving conserved glutamate and aspartate res...

Mucormycosis is a deadly infection which is caused by fungi of the order Mucorales including species belonging to the genus Rhizopus, Mucor, Mycocladus, Rhizomucor, Cunninghamella, and Apophysomyces. Despite antifungal therapy and surgical procedures, the mortality rate of this disease is about 90-100% which is exceptionally high. The hypersensitiv...

The problem of antibiotic resistance has prompted researchers around the globe to search for new antimicrobial agents. Antimicrobial proteins and peptides are naturally secreted by almost all the living organisms to fight infections and can be safer alternatives to chemical antibiotics. Lactoferrin (LF) is a known antimicrobial protein present in a...

The essential process of protein biosynthesis in the cell often gets stalled due to the premature abortion of the translation process and generates a byproduct of peptidyl-tRNA molecules. This defect is corrected by peptidyl-tRNA hydrolase (Pth) by hydrolyzing peptidyl-tRNA to yield tRNA and peptides. In order to understand the mechanism of catalyt...

Phosphopantetheine Adenylyltransferase (PPAT) is an enzyme that catalyzes the penultimate step in the biosynthesis of Coenzyme A (CoA), which is the active and physiologically functional form of dietary Vitamin B5. CoA serves as a cofactor for numerous metabolic reactions which makes it essential for cellular survival. This enzyme is also subject t...

Protein structure

Lactoperoxidase, a heme-containing glycoprotein, catalyzes the oxidation of thiocyanate by hydrogen peroxide into hypothio-cyanite which acts as an antibacterial agent. The prosthetic heme moiety is attached to the protein through two ester linkages via Glu258 and Asp108. In lactoperoxidase, the substrate-binding site is formed on the distal heme s...

Lactoperoxidase (LPO) is a heme containing oxido-reductase enzyme. It is secreted from mammary, salivary, lachrymal and mucosal glands. It catalyses the conversion of thiocyanate into hypothiocyanate and halides into hypohalides. LPO belongs to the superfamily of mammalian heme peroxidases which also includes myeloperoxidase (MPO), eosinophil perox...

Severe acute respiratory syndrome is a viral respiratory infection known as COVID-19, which is caused by a novel coronavirus, called SARS-associated coronavirus-2 (SARS-CoV-2). Considering it as an international concern, WHO declared COVID-19 as the “sixth public health emergency” and has termed it as ‘pandemic”. Currently, no specific drugs are av...

The recent pandemic caused by SARS-CoV-2 has led the world to a standstill, causing a medical and economic crisis worldwide. This crisis has triggered an urgent need to discover a possible treatment strategy against this novel virus using already-approved drugs. The main protease (Mpro) of this virus plays a critical role in cleaving the translated...

Background Type-III Pantothenate kinase from the multi drug resistant bacteria, Acinetobacter baumannii (AbPanK) catalyzes the first step of the essential Coenzyme A biosynthesis pathway. AbPanK is an attractive drug target against the bacteria since it is an essential enzyme and its structure is significantly different from the human PanK. Method...

The recent outbreak of the SARS-CoV-2 virus leading to the disease COVID 19, a global pandemic has resulted in an unprecedented loss of life and economy worldwide. Hence, there is an urgent need to discover effective drugs to control this pandemic. NSP16 is a methyltransferase that methylates the ribose 2′-O position of the viral nucleotide. Taking...

The recent outbreak of the SARS-CoV-2 virus leading to the disease COVID 19 has become a global pandemic that is spreading rapidly and has caused a global health emergency. Hence, there is an urgent need of the hour to discover effective drugs to control the pandemic caused by this virus. Under such conditions, it would be imperative to repurpose a...

SARS-CoV-2 is the causative agent of COVID-19 and has been declared as pandemic disease by World Health Organization. Lack of targeted therapeutics and vaccines for COVID-2019 have triggered the scientific community to develop new vaccines or drugs against this novel virus. Many synthetic compounds and antimalarial drugs are undergoing clinical tri...

Structural basis of working of mammalian heme lactoperoxidase

Crystal Structure of bovine lactoperoxidase with a partially linked heme moiety at 1.98 Å resolution

Phosphopantetheine adenylyl transferase catalyzes a rate limiting penultimate step of the multistep reaction which produces coenzyme A (CoA) as a final product. CoA is required as an essential cofactor in a number of metabolic reactions. Therefore inhibiting the function of this enzyme will lead to cell death in bacteria. Acinetobacter baumannii is...

Phosphopantetheine adenylyltransferase (PPAT, EC. 2.7.7.3) catalyzes an essential step in the reaction that transfers an adenylyl group from adenosine tri phosphate (ATP) to 4′-phosphopantetheine (pPant) yielding 3′- dephospho-coenzyme A (dPCoA) and pyrophosphate (PP) in the coenzyme A (CoA) biosynthesis pathway. The enzyme PPAT from Acinetobacter...

Ribosome inactivating protein (RIP) catalyzes the cleavage of glycosidic bond formed between adenine and ribose sugar of ribosomal RNA to inactivate ribosomes. Previous structural studies have shown that RNA bases, adenine, guanine, and cytosine tend to bind to RIP in the substrate binding site. However, the mode of binding of uracil with RIP was n...

Women with endometriosis (EMS) appear to be at a higher risk of developing other autoimmune diseases predominantly multiple sclerosis (MS). Though EMS and MS are evidently diverse in their phenotype, they are linked by a common autoimmune condition or immunodeficiency which could play a role in the expansion of endometriosis and possibly increase t...

Peptidyl-tRNA hydrolase (Pth) catalyzes the breakdown of peptidyl-tRNA into peptide and tRNA components. Pth from Acinetobacter baumannii ( Ab Pth) was cloned, expressed, purified and crystallized in native unbound ( Ab Pth-N) state and in bound state with phosphate ion and cytosine arabinoside (cytarabine) ( Ab Pth-C). Structures of Ab Pth-N and A...

The mammalian heme peroxidases including lactoperoxidase (LPO), myeloperoxidase (MPO), eosinophil peroxidase (EPO) and thyroid peroxidase (TPO) contain a covalently linked heme moiety. Initially, it was believed that the heme group was fully cross-linked to protein molecule through at least two ester linkages involving conserved glutamate and aspar...

A sequence alignment of horse cytochrome c (cyt c) with all known cyts c shows that Leu at position 94 is conserved, except in 14 species which have either Val or Ile at this position. It is also known that Leu94 of the mammalian cyt c plays an important role in folding and stability. The important question here is as to what will happen in terms o...

Lactoperoxidase (LPO) belongs to mammalian heme peroxidase superfamily which also includes myeloperoxidase (MPO), eosinophil peroxidase (EPO) and thyroid peroxidase (TPO). LPO catalyzes the oxidation of a number of substrates including thiocyanate while TPO catatalyzes the biosynthesis of thyroid hormones. LPO is also been shown to catalyze the bio...

?-glutamyl transpeptidase (GGT) catalyzes the transfer of the ?-glutamyl moiety from donor compounds such as L-glutamine (Gln) and glutathione (GSH) to an acceptor. During the biosynthesis of various ?-glutamyl-containing compounds using GGT enzyme, auto-transpeptidation reaction leads to the formation of unwanted byproducts. Therefore, in order to...

Lactoperoxidase (LPO) is a member of mammalian heme peroxidase superfmily whose other members are myeloperoxidase (MPO), eosinophil peroxidase (EPO) and thyroid peroxidase (TPO). In these enzymes, the heme moiety is linked to protein through two or three covalent bonds. In the mature LPO, the heme moiety is linked to protein through two ester bonds...

Dehydroquinase (3-dehydroquinate dehydratase, DHQD, EC 4.2.1.10) catalyzes the conversion of dehydroquinate to dehydroshikimate. DHQD from Acinetobacter baumannii (AbDHQD) was cloned, expressed and purified to homogeneity. The binding studies showed that two compounds quinic acid and citrazinic acid bound to AbDHQD at micromolar concentrations. AbD...

Lactoperoxidase (LPO, EC 1.11.1.7) is a member of the mammalian heme peroxidase family which also includes thyroid peroxidase (TPO). These two enzymes have a sequence homology of 76%. The structure of LPO is known but not that of TPO. In order to determine the mode of binding of antithyroid drugs to thyroid peroxidase, we have determined the crysta...

Table of contents O1 Regulation of genes by telomere length over long distances Jerry W. Shay O2 The microtubule destabilizer KIF2A regulates the postnatal establishment of neuronal circuits in addition to prenatal cell survival, cell migration, and axon elongation, and its loss leading to malformation of cortical development and severe epilepsy No...

The bilobal lactoferrin is a ∼76kDa glycoprotein. It sequesters two Fe3+ ions together with two CO32- ions. The C-terminal half (residues, Tyr342 - Arg689, C-lobe) of bovine lactoferrin (residues Ala1 - Arg689) was prepared by limited proteolysis using trypsin. Both C-lobe and intact bovine lactoferrin were saturated to 100%. Both of them retained...

The lipase enzyme converts long chain acyltriglycerides into di- and monoglycerides, glycerol and fatty acids. The catalytic site in lipase is situated deep inside the molecule. It is connected through a tunnel to the surface of the molecule. In the unbound state under aqueous conditions, the tunnel remains closed. The tunnel can be opened when the...

The type 1 ribosome inactivating protein from Momordica balsamina (MbRIP1) has been shown to interact with purine bases, adenine and guanine of RNA/DNA. We report here the binding and structural studies of MbRIP1 with a pyrimidine base, cytosine; cytosine containing nucleoside, cytidine; and cytosine containing nucleotide, cytidine diphosphate. All...

Allium sativum is well known for its medicinal properties. The A. sativum lectin 50 (ASL50, 50 kDa) was isolated from aged A. sativum bulbs and purified by gel filtration chromatography on Sephacryl S-200 column. Agar well diffusion assay were used to evaluate the antimicrobial activity of ASL50 against Candida species and bacteria then minimal inh...

Enteric fever is a major cause of morbidity in several parts of the Indian subcontinent. The treatment for typhoid fever majorly includes the fluoroquinolone group of antibiotics. Excessive and indiscriminate use of these antibiotics has led to development of acquired resistance in the causative organism Salmonella Typhi. The resistance towards flu...

The mammalian haem peroxidase superfamily consists of myeloperoxidase (MPO), lactoperoxidase (LPO), eosinophil peroxidase (EPO) and thyroid peroxidase (TPO). These enzymes catalyze a number of oxidative reactions of inorganic substrates such as Cl⁻, Br⁻, I⁻ and SCN⁻ as well as of various organic aromatic compounds. To date, only structures of MPO a...

Peptidyl-tRNA hydrolase (Pth) catalyses the release of tRNA and peptide components from peptidyl-tRNA molecules. Pth from a Gram-positive bacterium Streptococcus pyogenes (SpPth) was cloned, expressed, purified and crystallised. Three-dimensional structure of SpPth was determined by X-ray crystallography at 2.19 Å resolution. Structure determinatio...

Phospholipase A2 (PLA2) catalyzes the hydrolysis of phospholipids into arachidonic acid and lysophospholipids. Arachidonic acid is used as a substrate in the next step of the multistep pathway leading to the production of eicosanoids. The eicosanoids, in extremely low concentrations, are required in a number of physiological processes. However, the...

During the course of protein synthesis in the cell, the translation process often gets terminated due to various reasons. As a result of this, peptidyl-tRNA molecules are released which are toxic to the cell as well as it reduces the availability of free amino acid and tRNA molecules for the required protein synthesis in the cell. Such a situation...

Lactoperoxidase is a member of mammalian heme peroxidase superfamily that consists of lactoperoxidase (LPO), myloperoxidase (MPO), thyroid peroxidase (TPO), eosinophil peroxidase (EPO). So far crystal structures of only two mammalian peroxidases LPO and MPO have been determined. The structures of LPO have been determined from the samples obtained f...

Ribosome Inactivating Proteins (RIPs) are capable of inhibiting protein synthesis by catalytically hydrolyzing at specific purine residues from the sarcin / ricin loop of large ribosomal RNA. There are two types of RIPs: type 1 - RIPs (RIP-1) are single polypeptide chain proteins while type 2 - RIPs contain two polypeptide chains which are covalent...

Lactoperoxidase is a member of mammalian heme peroxidase superfamily that consists of lactoperoxidase (LPO), myloperoxidase (MPO), thyroid peroxidase (TPO), eosinophil peroxidase (EPO). So far crystal structures of only two mammalian peroxidases LPO and MPO have been determined. The structures of LPO have been determined from the samples obtained f...

Polo-like kinase (Plk)1 is a key regulator of the cell cycle during mitotic phase and is an attractive anti-mitotic drug target for cancer. Plk1 is a member of Ser/Thr kinase family which also includes Plk2-4 in human. Plk1 promotes the cell division whereas Plk2 and Plk3 are reported to act as tumour suppressors. The available inhibitors of Plk1 a...

Bovine lactoferrin, a 76‐ kD a glycoprotein (Ala1–Arg689) consists of two similar N‐ and C‐terminal molecular halves with the ability to bind two Fe ³⁺ ions. The N‐terminal half, designated as the N‐lobe (Ala1–Arg341) and the C‐terminal half designated as the C‐lobe (Tyr342–Arg689) have similar iron‐binding properties, but the resistant C‐lobe prol...

Peptidyl-tRNA hydrolase is an essential enzyme which acts as one of the rescue factors of the stalled ribosomes. It is an esterase that hydrolyzes the ester bond in the peptidyl-tRNA molecules, which are products of ribosome stalling. This enzyme is required for rapid clearing of the peptidyl-tRNAs, the accumulation of which in the cell leads to ce...

Lactoferrin is an 80 kDa bilobal, iron binding glycoprotein which is primarily antimicrobial in nature. The hydrolysis of lactoferrin by various proteases in the gut produces several functional fragments of lactoferrin which have varying molecular sizes and properties. Here, bovine lactoferrin has been hydrolyzed by trypsin, the major enzyme presen...

Pathogenesis related (PR) proteins are one of the major sources of plant derived allergens. These proteins are induced by the plants as a defense response system in stress conditions like microbial and insect infections, wounding, exposure to harsh chemicals, and atmospheric conditions. However, some plant tissues that are more exposed to environme...

Trypanosoma brucei Pteridine reductase (TbPTR1) is of vital importance and is an established drug target for dreaded Human African trypanosomiasis (HAT). Pharmacophore perception strategy has been employed to identify key chemical features responsible for the biological activity for TbPTR1. The findings suggest that three different pharmacophore fe...

Peptidyl-tRNA hydrolase is an essential enzyme which acts as one of the rescue factors of the stalled ribosomes. It is an esterase that hydrolyzes the ester bond in the peptidyl-tRNA molecules, which are products of ribosome stalling. This enzyme is required for rapid clearing of the peptidyl-tRNAs, the accumulation of which in the cell leads to ce...

Peptidoglycan recognition proteins belong to a broad family of innate immunity molecules. Mammals have four types of peptidoglycan recognition proteins designated as PGRP-S, PGRP-Iα, PGRP-Iβ and PGRP-L. PGRP-S is expressed in the granular polymorphonuclear leucocytes, PGRP-Iα is secreted from liver into blood and PGRP-Iβ, and PGRP-L are expressed i...

Chitinases are known to hydrolyze chitin polymers into smaller chitooligosaccharides. Chitinase from bacterium Serratia proteamaculans (SpChiD) is found to exhibit both hydrolysis and transglycosylation activities. SpChiD belongs to family 18 of glycosyl hydrolases (GH-18). The recombinant SpChiD was crystallized and its three-dimensional structure...

Lactoperoxidase (LPO) is a member of a large group of mammalian heme peroxidases that include myeloperoxidase (MPO), eosinophil peroxidase (EPO) and thyroid peroxidase (TPO). The LPO is found in exocrine secretions including milk. It is responsible for the inactivation of a wide range of micro-organisms and hence, is an important component of defen...

Several plant-derived allergens have been identified which result in the formation of immunoglobulin E antibodies. Primarily, these allergens belong to the protein families including seed storage proteins, structural proteins and pathogenesis-related proteins. Several allergens are also reported from flower bulbs which cause contact dermatitis. Suc...