Getting the Lead Out of Electronics

Background: Carbonic anhydrases (CAs) are physiologically important enzymes which participate in many gastrointestinal processes such as acid and bicarbonate secretion and metabolic pathways including gluconeogenesis and ureagenesis. The genomic data suggests that there are thirteen enzymatically active members of the mammalian CA isozyme family. In the present study, we systematically examined the mRNA expression levels of all known CA isozymes by quantitative real-time PCR in eight tissues of the digestive system of male and female mice. Results: The CAs expressed in all tissues were Car5b, Car7, and Car15, among which Car5b showed moderate and Car7 and Car15 extremely low expression levels. Car3, Car12, Car13, and Car14 were detected in seven out of eight tissues and Car2 and Car4 were expressed in six tissues. Importantly, Car1, Car3, and Car13 showed very high expression levels in certain tissues as compared to the other CAs, suggesting that these low activity isozymes may also participate in physiological processes other than CA catalysis and high expression levels are required to fulfil their functions in the body. Conclusion: A comprehensive mRNA expression profile of the 13 enzymatically active CAs in the murine gastrointestinal tract was produced in the present study. It contributes to a deeper understanding of the distribution of CA isozymes and their potential roles in the mouse digestive system. Background Mammalian α-carbonic anhydrases (CAs) are a large enzyme family containing 16 different isoforms, among which 13 (CA I, II, III, IV, VA, VB, VI, VII, IX, XII, XIII, XIV, and XV) are enzymatically active. The other three carbonic anhydrase-related proteins (CA-RP VIII, X, and XI) appear to lack CA activity because of substitutions in one or more of the functionally important histidine residues. In addition, the receptor-type protein-tyrosine phosphatases (RPTP) β and γ have been reported to contain 'CA-like' domains [1-3]. The enzymatically active CAs catalyze the reversible hydration of carbon dioxide in the reaction CO2 + H2O ⇔ HCO3 + H+, and participate in various biological processes, including CO2 transport, regulation of pH homeostasis, bone resorption, ureagenesis, gluconeogenesis, production of body fluids, and fertilization [1,4]. Each isozyme also has a characteristic subcellular localization. CA I, II, III, VII, and XIII are cytosolic, CA IV, IX, XII, XIV, and XV are membrane-associated, CA VA and VB are mitochondrial, and CA VI is secreted. According to a recent bioinformatic analysis, CA XV may be the last isoform of the mammalian CA gene family to be identified Published: 16 March 2007 BMC Molecular Biology 2007, 8:22 doi:10.1186/1471-2199-8-22 Received: 24 October 2006 Accepted: 16 March 2007 This article is available from: http://www.biomedcentral.com/1471-2199/8/22 © 2007 Pan et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.