Oxaloacetate decarboxylase activator

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,... 

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. 

Fig. 1. The diversity of anaplerotic enzymes present in Corynebacterium glutamicum. Numbers next to enzyme names represent typical in vitro activities in mU mg protein". Abbreviations PEPCk, phosphoenoipyruvate carboxykinase OAADc, oxaloacetate decarboxylase PyrCx, pyruvate carboxylase PEPCx, phosphoe o/pyruvate carboxylase...

Pathways 8-10 are all thermodynamically favorable and produce 1 mol of ATP. Malonyl-CoA and malonic-semialdehyde can be derived from oxaloacetate by employing novel enzymes, with CoA-dependent oxaloacetate dehydrogenase and 2-keto acid decarboxylase activity, respectively. Malate can be converted to 3-HP using a novel enzyme with malate decarboxylase activity (Figure 14.4). These enzymes do not exist in nature and, because of this, it has been proposed that malate decarboxylase activity can be created by enzyme engineering in order to increase their specificity toward oxaloacetate and ability to produce the metabolic intermediates [33]. 

Iversen T-G, Standal R, Pederson T, Caucheron DH (1994) IS 1032 from Acetobacter xylinunty a new mobile insertion sequence. Plasmid 32 46-54 Jabalquinto AM, Laivenieks M, Zeikus JG, Cardemil E (1999) Characterization of the oxaloacetate decarboxylase and pyruvate kinase-like activities of Saccha-romyces cerevisiae and Anaerobiospirillum succiniciproducens phospho-enolpyruvate carboxykinases. J Prot Chem 18 659-664 Jarvis L (2001) Lactic acid outlook up as polylactide nears market Chem Mark Repor 259(9) 5,14... 

This enzyme catalyses the decarboxylation of the ) -ketoacid oxaloacetate, with the same stoichiometry as acetoacetate decarboxylase. The former however, requires a Mn ion for activity and is insensitive to the action of sodium borohydride. This duality of mechanism is not unlike the one observed for enzymatic aldol condensation, where enzymes of Class 1 react by forming Schiff-base intermediates, whereas enzymes of Class II show metal ion requirements [47]. Oxaloacetate decarboxylase from cod also catalyses the reduction by borohydride of the enzymatic reaction product pyruvate. This is evidenced by the accumulation of D-lactate in presence of enzyme, reducing agent, and manganous ions. It has been proposed that both reduction and decarboxylation occur by way of an enzyme-metal ion-substrate complex in which the metal ion acts as an electron sink, thereby stabilizing the enolate ion formed in the decarboxylation reaction [48] ... 

Malonate decarboxylase (EC 4.1.1.88) and citrate lyase (EC 4.1.3.6) are both large enzyme complexes that consist of multiple subunits, the smallest of which acts as an ACP. These two complexes catalyze the decarboxylation of malonate to acetate and CO2 and the Mg -dependent cleavage of citrate to acetate and oxaloacetate, respectively. Both have been shown to require a thiol-containing prosthetic group for activity. However, unlike the carrier proteins described in the previous section, the ACP subunits of these proteins are not phosphopantetheinylated by a reaction with CoA. Instead, they rely on a unique cofactor, 2 -(5"-triphosphoribosyl)-3 -dephospho-CoA (24, dePCoA-RibPPP), as source of a 2 -(5"-phosphoribosyl)-3 -dephospho-CoA prosthetic group, which is bound to a conserved serine residue of the ACP. ° ° A similar prosthetic group has been identified in citramalate lyase (EC 4.1.3.22). The proposed biosynthesis and subsequent transfer reactions of the cofactor 24 to the ACPs of these complexes are shown in Scheme 5. 

---