Article

Characterization of CA XIII, a Novel Member of the Carbonic Anhydrase Isozyme Family

University of Florence, Florens, Tuscany, Italy
Journal of Biological Chemistry (Impact Factor: 4.57). 02/2004; 279(4):2719-27. DOI: 10.1074/jbc.M308984200
Source: PubMed

ABSTRACT The carbonic anhydrase (CA) gene family has been reported to consist of at least 11 enzymatically active members and a few
inactive homologous proteins. Recent analyses of human and mouse databases provided evidence that human and mouse genomes
contain genes for still another novel CA isozyme hereby named CA XIII. In the present study, we modeled the structure of human
CA XIII. This model revealed a globular molecule with high structural similarity to cytosolic isozymes, CA I, II, and III.
Recombinant mouse CA XIII showed catalytic activity similar to those of mitochondrial CA V and cytosolic CA I, with kcat/Km of 4.3 × 107 m–1 s–1, and kcat of 8.3 × 104 s–1. It is very susceptible to inhibition by sulfonamide and anionic inhibitors, with inhibition constants of 17 nm for acetazolamide, a clinically used sulfonamide, and of 0.25 μm, for cyanate, respectively. Using panels of cDNAs we evaluated human and mouse CA13 gene expression in a number of different tissues. In human tissues, positive signals were identified in the thymus, small
intestine, spleen, prostate, ovary, colon, and testis. In mouse, positive tissues included the spleen, lung, kidney, heart,
brain, skeletal muscle, and testis. We also investigated the cellular and subcellular localization of CA XIII in human and
mouse tissues using an antibody raised against a polypeptide of 14 amino acids common for both human and mouse orthologues.
Immunohistochemical staining showed a unique and widespread distribution pattern for CA XIII compared with the other cytosolic
CA isozymes. In conclusion, the predicted amino acid sequence, structural model, distribution, and activity data suggest that
CA XIII represents a novel enzyme, which may play important physiological roles in several organs.

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    • "They catalyze the reversible reaction: CO 2 þ H 2 O , HCO À 3 þ H þ (Sly and Hu 1995). To date, 16 isoforms have been characterized, 13 of which have been found to be enzymatically active (Hilvo et al. 2005; Kivela et al. 2005; Lehtonen et al. 2004; Pastorekova et al. 2004). Since several isozymes are expressed in the same cells and tissues, they may be mutually complementary to each other in physiological processes , and their regulation may be at least partly interconnected (Pan et al. 2006). "
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    ABSTRACT: Carbonic anhydrase VI (CAVI) is the only secreted isozyme of the α-carbonic anhydrase family, which catalyzes the reversible reaction [Formula in text]. It appears that CAVI protects teeth and gastrointestinal mucosa by neutralizing excess acidity. However, the evidence for this physiological function is limited, and CAVI may have additional functions that have yet to be discovered. To explore the functions of CAVI more fully, we generated Car6 (-/-) mice and analyzed Car6 (-/-) mutant phenotypes. We also examined transcriptomic responses to CAVI deficiency in the submandibular gland, stomach, and duodenum of Car6 (-/-) mice. Car6 (-/-) mice were viable and fertile and had a normal life span. Histological analyses indicated a greater number of lymphoid follicles in the small intestinal Peyer's patches. A total of 94, 56, and 127 genes were up- or down-regulated in the submandibular gland, stomach, and duodenum of Car6 (-/-) mice, respectively. The functional clustering of differentially expressed genes revealed a number of altered biological processes. In the duodenum, the significantly affected biological pathways included the immune system process and retinol metabolic processes. The response to oxidative stress and brown fat cell differentiation changed remarkably in the submandibular gland. Notably, the submandibular gland, stomach, and duodenum shared one important transcriptional susceptibility pathway: catabolic process. Real-time PCR confirmed an altered expression in 14 of the 16 selected genes. The generation and of Car6 (-/-) mice and examination of the effects of CAVI deficiency on gene transcription have revealed several affected clusters of biological processes, which implicate CAVI in catabolic processes and the immune system response.
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    • "The CA isozymes differ in several important characteristics, such as kinetic properties, susceptibility to inhibitors, and subcellular localization. The α-CA gene family has been reported to include at least 13 active isoforms with different structural and catalytic properties [1] [2] [3] [4] [5]. CA isozymes II, IX and XII have been extensively studied for their important role as promising biomarkers in different tumors, for example astrocytic tumors [5] [6] [7]. "
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    ABSTRACT: Carbonic anhydrase VII (CA VII) is a cytosolic enzyme expressed in several organs, including the human brain, but it has not been investi-gated earlier in any tumors. We designed the present study to evaluate CA VII expression in a cohort of human diffuse astrocytomas, mixed oligoastrocytomas and oligodendrogliomas. CA VII immunostaining was correlated to clinico-pathologic findings, survival data, and expres-sion of other molecular factors, including Ki-67, p53 protein and epidermal growth factor recep-tor. CA VII-positive staining was observed in 94% of astrocytomas and 85% of oligodendrog-liomas. In the tumor specimens, strong positive areas were often located in close proximity to necrosis. The CA VII immunoreactivity showed positive correlation with tumor malignancy grades of astrocytomas (p = 0.02, chi-square test). In all tumor categories, CA VII-positive staining was often seen in the endothelial cells of neovessels in addition to the tumor cells. CA VII intensity showed no significant association with p53 nor did it correlate with the amplification of epi-dermal growth factor receptor (analyzed only in astrocytomas) or cell proliferation. Our present results show that CA VII may act as a useful biomarker in histopathologic diagnostics of gliomas. The high expression of CA VII in the tumor cells and endothelium suggests impor-tant roles for the enzyme in tumor metabolism. The results also led us to conclude that CA VII might serve as a marker of poor prognosis in diffuse astrocytomas.
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    • "qRT-PCR revealed the most prominent signal for Car13, a recently discovered member of the CA family, which encodes a cytosolic isozyme with low catalytic activity (Lehtonen et al. 2004). Expression of Car13 mRNA has been reported in the mouse spleen, lung, kidney, heart, brain, skeletal muscle, and testis, as well as embryos of different developmental stages (Lehtonen et al. 2004). We have also reported high expression of Car13 mRNA in the mouse digestive tract, where its wide distribution suggests an important though yet undefined role (Pan et al. 2007). "
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