Properties of the glyceraldehyde-3-P dehydrogenase in heterocysts and vegetative cells of cyanobacteria

Simultaneous Occurrence of Two Different Glyceraldehyde-3-Phosphate Dehydrogenases in Heterocystous N2-Fixing Cyanobacteria

“…On the other hand, the NAD-dependent/NADP-dependent GAPDH specific activity ratio was near 1 in the extracts of vegetative cells (Table 1), as was also the case for crude extracts from Anabaena grown in media with nitrate or ammonia (data not shown) (24), thus suggesting that GAPDH2-which exhibits very similar activity of reduction with either nucleotide (12)-should account for most G3P dehydrogenase activity in these cells, as was reported for non-diazotrophic cyanobacteria (12,22). In contrast, the NAD-dependent/NADPdependent GADPH specific activity ratio was clearly higher than 1 in the heterocysts extracts (Table 1), in agreement with previous data (6,24,25). On the other hand, in all extracts the NADH oxidative reaction rate was higher (up to 2.5 times) than the NAD reductive one.…”

“…An intense carbohydrate degradation occurs in these cells to maintain the high respiratory activity required for an optimal nitrogenase function (3,4). Although D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity has been detected in both heterocysts and vegetative cells from several filamentous cyanobacteria (2,(5)(6)(7), no other aspects related to the characteristics of the enzyme, a key component of central carbon metabolism, are known. The recent finding in diverse cyanobacteria-some of them heterocystous strains-of three paralogous gap genes (gap1, gap2, and gap3) encoding potentially different GAPDHs has raised questions about their physiological roles (8 -10), in particular with regard to the possible gap gene product(s) functioning in the heterocyst.…”

A comparison of proline, thiol levels and GAPDH activity in cyanobacteria of different origins facing temperature-stress

“…The vital metabolic role of the enzyme is in the glycolytic transformation of glucose to pyruvic acid, the event highly crucial to carbohydrate metabolism (Harris & Waters 1976). Analogous report in cyanobacteria is limited to one by Papen et al (1986), who reported GAPDH in heterocyst and vegetative cells of Anabaena variabilis, A. cylindrica and Anabaena 7119 that utilized both NAD and NADP + for its activity. The NADP + -dependent enzyme activity in extract of whole filaments was 74 nmol min )1 mg )1 protein in A. variabilis, 61 nmol min )1 mg )1 protein in A. cylindrica and 85 nmol min )1 mg )1 protein in Anabaena 7119.…”

“…GAPDH (glyceraldehyde-3-phosphate dehydrogenase) has been reviewed extensively (Wrba et al 1990) and is a key enzyme involved in glycolysis, gluconeogenesis and the carbon reduction cycle in microbes (Leuschner & Antranikian 1995) including cyanobacteria (Papen et al 1986). Studies on homologous enzymes/proteins from organisms with different temperature optima are imperative in deciphering the acclimation process (van der Oost et al 1996).…”

Nitrogen Fixation and Hydrogen Metabolism in Cyanobacteria

“…Its further degradation is hampered by the fact that the tricarboxylic acid cycle is incomplete in cyanobacteria because neither an oxoglutarate dehydrogenase complex nor an oxoglutarate:ferredoxin oxidoreductase is present (208), which has been confirmed by recent large-scale proteomic studies (162,163). This prevents the complete degradation of the C2 moiety to CO 2 and NAD(P)H. Cyanobacteria apparently prefer to utilize NADP ϩ rather than NAD ϩ in catabolism (51), since several enzymes, such as isocitrate dehydrogenase (165) and glyceraldehyde-3-phosphate-dehydrogenase (166), are NADP ϩ rather than NAD ϩ dependent. In darkness, most cyanobacteria have to generate their energy via the oxidative pentose phosphate pathway: pyruvate, pyruvate: ferredoxin oxidoreductase, reduced ferredoxin, FNR, and NADPH (Fig.…”