Carboxy-lyases

Schutzbach, J. S., Feingold, D. S. Biosynthesis of uridine diphosphate D-xylose. IV. Mechanism of action of uridine diphosphoglucuronate carboxy-lyase. J. Biol. Chem. 245, 2476-2482 (1970). 

Thiamin (vitamin Bi, 22) (Fig. 14) - an important cofactor of decarboxylases, transketolases, carboxy-lyases, and some other enzymes - was successfully glycosylated by enzymatic transglycosylation using p-galactosidase [59] and p-A-acetyl-hexosaminidase [60] from A. oryzae. 

The role that the malo-lactic reaction—the decarboxylation of malic acid—plays in the overall physiology of the cell, and the enzymatic pathway of the reaction are two questions which have plagued enologists since the discovery of the reaction. Morenzoni (71) has described this discovery by Ochoa and coworkers (72, 73, 74), and he has related how their early representation of the reaction led to some confusion. We are now convinced, from studies by Radler and coworkers (75, 76) with partly purified enzymes from Lactobacillus and Leuconostoc, that the reaction is catalyzed by an inducible malate carboxy lyase with NAD (nicotinamide adenine dinucleotide) and Mn2+ as cofactors ... 

NADH as an end product. This implicates oxidized malic acid, either pyruvic or oxaloacetic acid, as another end product. By adding commercial preparations of L-lactic dehydrogenase or malic dehydrogenase to the reaction mixture, Morenzoni (90) concluded that the end product was pyruvic acid. Attempts were then made to show whether two enzymes—malate carboxy lyase and the classic malic enzyme, malate oxidoreductase (decarboxylating), were involved or if the two activities were on the same enzyme. The preponderance of evidence indicated that only one enzyme is involved. This evidence came from temperature inactivation studies, heavy-metal inhibition studies, and ratio measurements of the two activities of partially purified preparations of Schiitz and Radlers malo-lactic enzyme (76, 90). This is not the first case of a single enzyme having two different activities (91). 

Our work (6, 7, 8) has shown that the same protein which causes the malic acid-lactic acid transformation will also cause the production of a small amount of pyruvic acid from malic acid. However, the pyruvic acid produced is not involved with lactic acid production. Apparently, one protein is producing two end products from the same substrate. The malic acid to lactic acid activity is not an oxidoreductase whereas the malic acid to pyruvic acid activity is. Since the pyruvic acid producing activity is only a small per cent (about 0.2%) of the malic acid to lactic acid activity, and since the enzyme should be classified according to the major end product, the enzyme has been given the trivial frame of malo-lactic enzyme (6, 7, 8). Schiitz (28) has speculated that if this enzyme were crystallized, it should be called malate-carboxy-lyase. In either case, use of either the trivial or accepted terms for the malic enzyme is not recommended. 

Figure 10. Reaction mechanism for UDP-GA carboxy-lyase (D. S. Feingold et al.)...

Several enzymes involved in the biosynthesis of phenethylamines in plants have been studied. A tyrosine carboxy-lyase (decarboxylase) isolated from barley seedlings and barley roots has been studied in considerable detail (347-349). The enzyme is rather specific for L-tyrosine and meta-tyrosine ort/io-tyrosine and L-dopa are decarboxylated slowly. Tyrosine carboxylase activity was also demonstrated in wheat and maize (348). Cytisus scoparius contains dopa car-boxy-lyase which decarboxylates d- and L-dopa at about the same rate (350). Tyrosine is decarboxylated 15 times slower. A similar enzyme has been found in the alga Monostroma juscum (174). 

Kobayashi, M., Nakagawa, H., Suda, I., Miyagawa, I., and Matoh, T., 2002, Purification and cDNA cloning of UDP-D-glucuronate carboxy-lyase (UDP-D-xylose synthase) from pea seedlings. Plant Cell Physiol. 43 1259-1265. 

A number of ubiD mutants studied formed about 20% of the wild-type levels of Q, indicating that either the mutants are leaky or there is an alternate enzyme for the reaction. However, the significance of any alternate carboxy-lyase in the wild-type strains has been questioned. ... 

DOPA decarboxylase 3,4-dihydroxy-L-phenylalanine carboxy-lyase (EC4.1.1.26)... 

Aromatic L-amino acid decarboxylase Aromatic L-amino acid carboxy-lyase. 

In further consideration of the biosynthesis of the piperidine alkaloids the question of the significance of the incorporation of cadaverine must be answered. Accordingly further research has been directed to this point and it has been shown that cadaverine is a normal component of S. acre, that it is a specific precursor of sedamine (20), and that it is formed from lysine at the same time as sedamine. It follows then that any scheme for the biosynthesis of the piperidine alkaloids which does not accommodate cadaverine as a normal component is unrealistic An eminently reasonable hypothesis which fits all the evidence is shown in Scheme 1 it was anticipated in last year s Report. For those alkaloids derived from lysine without the intervention of a symmetrical intermediate, cadaverine formed by decarboxylation of lysine must remain enzyme-bound and therefore unsymmetrical. Exogenous cadaverine enters the pathway at this point by absorption on to the enzyme to give (29). In order to explain the incorporation of lysine into some alkaloids by way of a symmetrization step it is necessary only to postulate equilibration of bound with unbound cadaverine. The proposal that pyridoxal phosphate is involved in this pathway is more than mechanistically attractive, for L-lysinedecarboxylase (EC 4.1.1.18, L-lysine carboxy-lyase) and diamine oxidase [EC 1.4.3.6, diamine oxygen oxidoreductase (deaminating)], the two enzymes whose participation in the conversion of lysine into A -piperideine (30) is likely, both require pyridoxal phosphate as a co-factor. 

There is an alternative way of viewing the above results, however. It could be that the biosynthetic pathway to the pyrrolidine ring of nicotine is similar (in part) to the route to the piperidine alkaloids. Part of the model suggested for the biosynthesis of the piperidine nucleus from lysine (see above) could be easily adapted to account for the C02 and nornicotine results, that is variable/in-complete equilibration of bound putrescine (arising by enzyme-mediated decarboxylation of ornithine) with unbound material. L-Ornithine decarboxylase (EC 4.1.1.17, L-ornithine carboxy-lyase) occurs widely in higher plants and like L-lysine decarboxylase requires pyridoxal phosphate as a co-factor. ... 

Orotidyhc acid decarboxylase (orotidine 5 -phosphate carboxy-lyase, EC 4.1.1.23) catalyses the only irreversible step in the pyrimidine synthesis de novo. The enzyme is competitively inhibited by UMP and CMP [114-116] and some anomalous pyrimidine nucleoside 5 -monophosphates. The activity of orotidylic acid decarboxylase in excess of that of orotate phosphoribosyltransferase accounts for the absence of orotidine 5 -phosphate in the pool of low molecular weight compounds in animal cells. 

Orotidine-5 -phosphate carboxy-lyase Orotidine-5 -phosphate decarboxylase... 

Hartmann T (1972) Leucine carboxy-lyase of marine Rhodophyceae occurrence distribution and some properties. Phytochemistry 11 1327-1336... 

The location of the incorporated tritium was established by (1) conversion of the nucleotide sugars to UDP-glucuronic acid by UDP-glucose dehydrogenase, (2) decarboxylation to UDP-xylose by UDP-glucuronate carboxy-lyase, and (3) unequivocal chemical degradation of the xylose moiety to determine the position of the label. The procedures used showed conclusively that the label was located on G—4 of the hexose and it was thus evident that a 4-keto intermediate was indeed formed during epimerization. 

Biogenic amines are formed from amino acids by the action of carboxy-lyases (decarboxylases containing as a cofactor pyridoxal 5 -phosphate), or arise from amino adds and carbonyl compounds by the action of transaminases (see Section 8.2.10.1.2). The so-called endogenous biogenic amines are the products of metabohsm and at low concentrations are natural components of almost aU foods. Exogenous biogenic amines are formed in foods as a result of microbial contamination and fermentation processes. 

J.G.Jacobsen, L.L. Thomas and L.H. Smith, Jr., Properties and distribution om mammalian L-cysteine sulfinate carboxy-lyases, Biochim. Biophvs. Acta 85 103 (196 ). 

Jacobsen, J. G., Thomas, L. L., and Smith, L. H., Jr., 1964, Properties and distribution of mammalian L-cysteine sulfinate carboxy-lyases, Biochem. biophys. Acta (Amst.), 85 103. 

Another reaction to isobutene is through decarboxylation and subsequent dehydration of 3-hydroxyisovalerate (3-hydroxy-3-methylbutyrate), catalysed by mevalonate diphosphate decarboxylase (MDD, EC 4.1.1.33) (Gogerty and Bobik 2010 Marliere 2010). This enzyme, from the class of carboxy-lyases, is part of terpenoid or ergosterol biosynthesis, and isobutene formation is its side reaction. Even though the MDD family of enzymes is present in many microorganisms, none of them are known to synthesise isobutene (van Leeuwen et al. 2012 Bloch et al. 1959) (Fig. 4). 

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