In mammals various α-CA isoforms with different subcellular localization and tissue distribution are implicated in many physiological processes such as carboxylation/decarboxylation GDC 941 reactions, transport of CO2 and/or HCO3-, pH regulation, ion exchange, calcification, see more metabolism of urea, glucose and lipids, tumorigenicity, bone resorption and many other physiological and pathological processes [5]. Members of β-CAs are predominant in

plants, algae, archaea and bacteria. In photosynthetic organisms β-CAs play an important role in transport and autotrophic fixation of CO2 while in prokaryotes β-CAs are involved in wide range of cellular functions including provision of HCO3 – for carboxylating enzymes which catalyze key steps in biosynthetic pathways for essential metabolites, such as amino acids, nucleotides, fatty acids [6, 7]. The γ-CAs are predominant in bacteria and archaea domains. In eukaryotes, they have so far been described only in photosynthetic organisms. While the physiological role of α-CAs in mammals and β-CAs in plants and prokaryotes, have been extensively studied, the role of γ-CAs remain elusive. To date, the only γ-CA that has been extensively characterized is “”Cam”" from the methanogenic CHIR-99021 ic50 archaeon Methanosarcina thermophila [8, 9]. In the

cyanobacterium Synechocystis, the bifunctional CcmM protein localized in carboxysome (structure involved in CO2 concentration) shows an N-terminal γ-CA like domain which has been proposed to bind HCO3 Palmatine -/CO2 [10]. However, no carbonic anhydrase activity could be detected for the recombinant CcmM expressed in E. coli. Recently, a similar role for binding and transporting bicarbonate has been proposed for γ-CA subunits of plant mitochondrial complex, suggesting that the so-called γ-CAs in photosynthetic

eukaryotic organisms do not act as carbonic anhydrases but may have related activity contributing to CO2 recycling in photorespiration, or play a role in the carbon transport between mitochondria and chloroplasts to increase the efficiency of photosynthetic CO2 fixation [11]. Unraveling of microbial genome sequences has shown that γ-CAs are widespread in prokaryotes, and it is likely that these enzymes play diverse roles in microorganisms. Investigations into the ways in which archaea and bacteria domains use γ-carbonic anhydrase may reveal novel aspects of prokaryotic physiology. We are analyzing the role of carbonic anhydrases in a nonphotosynthetic, Gram-negative, plant growth promoting α-proteobacterium, Azospirillum brasilense that lives in close association with the roots of several important crop plants and grasses and stimulates the growth of its host plant by producing phytohormones and siderophores [12]. Earlier, we have cloned the gene encoding β-CA from A. brasilense, overexpresed, purified and characterized β-CA. We also showed that the transcription of bca gene was down regulated by stationary phase, elevated CO2 and acidic pH [13].