Decarboxylases oxaloacetate decarboxylase

Decarboxylases. Pour decarboxylases, methylmalonyl-CoA decarboxylase, oxaloacetate decarboxylase, glutaconyl-CoA decarboxylase, and malonate decarboxylase, are encountered in anaerobic procaryotes. These biotin-dependent enzymes do not require ATP, are membrane bound, and are coupled to sodium... 

Kosicki, G. W., Westheimer, F. H. Oxaloacetate decarboxylase from cod. Mechanism of action and stereoselective reduction of pyruvate by borohydride. Biochemistry 7, 4303—4309 (1968). 

OVERSATURATION OXALOACETATE DECARBOXYLASE Oxaloacetate, synthesis in gluconeogenesis, PYRUVATE CARBOXYLASE PHOSPHOENOLPYRUVATE CARBOXYKI-NASE (PYROPHOSPHATE)... 

It was reported (14) that the adaptive enzyme from Lactobacillus plantarum could decarboxylate oxaloacetic acid as well as malic acid. However, in the same organism, Nathan (30) carried this work further and showed that the oxaloacetate decarboxylase activity is not related at all to the malic acid-lactic acid transformation activity. She based this conclusion on the ability of malic and oxaloacetic acids to induce oxaloacetate decarboxylase activity as well as malic enzyme activity. In her words,... 

Oxaloacetate is also decarboxylated without phosphorylation of the enolate anion formed but with release of free pyruvate. Both pyruvate kinase and PEPCK can act as oxaloacetate decarboxylases.261... 

Oxaloacetate decarboxylase Methylmalonyl-CoA decarboxylase Glutaconyl-CoA decarboxylase... 

Biotin has been shown to be an essential component of a bacterial oxaloacetate decarboxylase that pumps two sodium ions out of a cell for each oxaloacetate molecule decarboxylated. Propose a chemical mechanism for the functioning of biotin and also any ideas that you may have for the operation of the sodium pump. 

A very large number of enzymes show an absolute requirement for a monovalent cation for catalytic activity, and for most of these K+ is most effective.90,91 Usually Na+ is inactive but a small number of enzymes [apart from (Na+, K+)-ATPase] have a specific requirement for Na+, such as oxaloacetate decarboxylase.92 The oxidation of NAD-linked substrates by the aerobic marine bacterium Alteromonas haloplanktis requires the presence of Na+.93 Monovalent ions other than Na+ can usually replace K+ but with lowered activity. The Rb+ cation usually substitutes quite effectively, but there has been much interest in replacing K+ with Tl+, in order to exploit the NMR properties of the latter cation. T + sometimes causes inhibition, as it binds more strongly than K+ and sometimes to additional sites, reflecting its soft chemical character. On occasions Tl+ may activate an enzyme more effectively than the native K+. Some examples of enzymes activated by monovalent cations are given in Table 5. 

Other types of enzymes When no oxidase or dehydrogenase is available for a target analyte, other types of enzymes have been used for biospedfic recognition e.g. for citric acid detection, citrate lyase, and amperometric detection was possible by coupling to two more enzymatic reactions oxaloacetate decarboxylase and pyruvate oxidase, which convert citric add into H2O2 with the latter being monitored amperometrically with an H202 probe. For detection of acetic add, acetate kinase is used, coupled to pyruvate kinase and pyruvate oxidase [34,35]. 

Prodromidis et al. [35] Citric acid Fruits, juices and sport drinks Citrate lyase (in solution), oxaloacetate decarboxylase and pyruvate oxidase/ sandwiched between a cellulose acetate membrane and a protective polycarbonate membrane H202 probe (Pt electrode) ... 

The successive determination of both transaminases has also been carried out with a sequence electrode containing oxaloacetate decarboxylase and pyruvate oxidase (Kihara et al., 1984b). The enzymes were coadsorbed on a PVC membrane of 40 pm thickness in the presence of thiamine pyrophosphate, FAD, and MgC. ... 

It may be observed that, for the cycle to revolve, a supply of oxaloacetic acid is required with which the acetyl-CoA can react. Of course, oxaloacetic acid is being constantly re-formed as each revolution of the cycle is completed, but, nonetheless, it is not surprising to find that many cells, especially in bacteria, take precautions against running out of so essential a primer by having an alternative source of oxaloacetic acid. The alternative source is provided by an enzyme, oxaloacetic decarboxylase which catalyses the direct fixing of carbon dioxide on to pyruvic acid to form oxaloacetic acid as in equation (24) ... 

Table 12.7-1. Time course for the transamination of phenylpyruvate to L-phenylalanine in the presence and absence of oxaloacetate decarboxylase.

Reaction time (min) Transaminase alone Phenylpyruvate (mM) Transaminase Oxaloacetate decarboxylase Phenylpyruvate (mM)... 

The decarboxylation reaction catalyzed by the enzyme oxaloacetate decarboxylase has been examined using enzymes from four different sources Pseudomonas putida, Micrococcus luteus, and two strains of Azotobacter vinelandii. The highest rates were obtained with the oxaloacetate decarboxylase isolated from Pseudomonas, a Mg2+-requiring enzyme17, 121. 

The decarboxylation of oxaloacetate is catalyzed by oxaloacetate decarboxylase [Eq. (7)] from a variety of species. 

The enzyme requires a divalent metal ion (18) but has no other cofactors. The decarboxylation is invariably stereospecihc, but some oxaloacetate decarboxylases operate with retention of configuration and some operate with inversion (79). 

The mechanism of the enzymic decarboxylation of oxaloacetate presumably resembles that of the metal ion-catalyzed reaction (Scheme III), in which the enzyme-bound metal chelates to the a-carboxyl and the keto carbonyl of the substrate prior to decarboxylation (cf. Scheme II). Interestingly, an enzyme identified as oxaloacetate decarboxylase was later identified as pyruvate kinase... 

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