Emma Farrell

Publications (3) View all

• Article: Functional Characterization of AlgL, an Alginate Lyase from Pseudomonas aeruginosa.

  Emma K Farrell, Peter A Tipton
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  ABSTRACT: Abstract Alginate lyase (AlgL) catalyzes the cleavage of the polysaccharide alginate through a β-elimination reaction. In Pseudomonas aeruginosa algL is part of the alginate biosynthetic operon, and although it is required for alginate biosynthesis, it is not clear why. Steady-state kinetic studies were performed to characterize its substrate specificity, and revealed that AlgL operates preferentially on non-acetylated alginate or its precursor mannuronan. Mature alginate is secreted as a partially acetylated polysaccharide, so this observation is consistent with suggestions that AlgL serves to degrade mislocalized alginate that is trapped in the periplasmic space. The kcat/Km for the reaction increased linearly with the number of residues in the substrate, from 2.1x105 M-1s-1 for substrate containing 16 residues to 7.9x106 M-1s-1 for substrate with 280 residues. Over the same substrate size range, kcat varied between 10 s-1 and 30 s-1. The variation in kcat/Km with substrate length suggests that AlgL operates in a processive manner. AlgL displayed a surprising lack of stereospecificity, in that it was able to catalyze cleavage adjacent to either mannuronate or guluronate residues in alginate. Thus, the enzyme is able to remove the C5 proton from both mannuronate and guluronate, which are C5 epimers. Exhaustive digestion of alginate by AlgL generated dimeric and trimeric products, which were characterized by 1H NMR spectroscopy and mass spectrometry. Rapid-mixing chemical quench studies revealed that there was no lag in dimer or trimer production, indicating that AlgL operates as an exopolysaccharide lyase.
  Biochemistry 12/2012; · 3.42 Impact Factor
• Article: Primary fatty acid amide metabolism: conversion of fatty acids and an ethanolamine in N18TG2 and SCP cells.

  Emma K Farrell, Yuden Chen, Muna Barazanji, Kristen A Jeffries, Felipe Cameroamortegui, David J Merkler
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  ABSTRACT: Primary fatty acid amides (PFAM) are important signaling molecules in the mammalian nervous system, binding to many drug receptors and demonstrating control over sleep, locomotion, angiogenesis, and many other processes. Oleamide is the best-studied of the primary fatty acid amides, whereas the other known PFAMs are significantly less studied. Herein, quantitative assays were used to examine the endogenous amounts of a panel of PFAMs, as well as the amounts produced after incubation of mouse neuroblastoma N(18)TG(2) and sheep choroid plexus (SCP) cells with the corresponding fatty acids or N-tridecanoylethanolamine. Although five endogenous primary amides were discovered in the N(18)TG(2) and SCP cells, a different pattern of relative amounts were found between the two cell lines. Higher amounts of primary amides were found in SCP cells, and the conversion of N-tridecanoylethanolamine to tridecanamide was observed in the two cell lines. The data reported here show that the N(18)TG(2) and SCP cells are excellent model systems for the study of PFAM metabolism. Furthermore, the data support a role for the N-acylethanolamines as precursors for the PFAMs and provide valuable new kinetic results useful in modeling the metabolic flux through the pathways for PFAM biosynthesis and degradation.
  The Journal of Lipid Research 11/2011; 53(2):247-56. · 5.56 Impact Factor
• Article: Biosynthesis, degradation and pharmacological importance of the fatty acid amides.

  Emma K Farrell, David J Merkler
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  ABSTRACT: The identification of two biologically active fatty acid amides, N-arachidonoylethanolamine (anandamide) and oleamide, has generated a great deal of excitement and stimulated considerable research. However, anandamide and oleamide are merely the best-known and best-understood members of a much larger family of biologically occurring fatty acid amides. In this review, we will outline which fatty acid amides have been isolated from mammalian sources, detail what is known about how these molecules are made and degraded in vivo, and highlight their potential for the development of novel therapeutics.
  Drug Discovery Today 08/2008; 13(13-14):558-68. · 6.83 Impact Factor