Decarboxylase enzyme

The resolving of a variety of a-substituted carboxyHc acid esters by a previously undescribed enzyme, Candida lipolytica esterase, has been reported (64). a-Methyl-a-amino (49) and a-methyl-a-hydrazino (48) esters, which function as inhibitors of acid decarboxylase enzymes, are obtained on a multigram scale in optically pure form. 

The product of the hydroxylation of tryptophan, 5-hydroxytryptophan, is rapidly decarboxylated to 5-HT by a specific decarboxylase enzyme. This is generally thought to be a soluble enzyme which suggests that 5-HT is synthesised in the cytoplasm, before it is taken up into the storage vesicles. If this is the case, then considerable losses might be incurred from its metabolism by monoamine oxidase before it reaches the storage vesicles. Indeed, this could explain why 5-HT turnover seems to greatly exceed its rate of release. 

The high affinity of the decarboxylase enzyme for its substrate (10 pM in the brain) makes it unlikely that this stage could ever become rate-limiting for the pathway as a whole. Nevertheless, the for this enzyme is considerably higher than tissue concentrations of 5-hydroxytryptophan and so, again, supply of this substrate is likely to be a crucial factor. 

Hilbi H, R Hermann, P Dimroth (1993) The malonate decarboxylase enzyme system of Malonomonas rubra evidence for the cytoplasmic location of the biotin-containing component. Arch Microbiol 160 126-131. 

Pyruvate carboxylase is a mitochondrial enzyme and like other carboxylase or decarboxylase enzymes requires biotin as coenzyme. The biotin is firmly attached to the enzyme protein (i.e. a prosthetic group) via a lysine residue. The role of biotin is to hold the C02 in the correct orientation to allow its incorporation into the pyruvate. 

Pyridoxine (vitamin Bg, 18) (Fig. 13) assists in the balancing of sodium and potassium as well as promoting red blood cell production. A lack of pyridoxine can cause anemia, nerve damage, seizures, skin problems, and sores in the mouth. It is required for the production of the monoamine neurotransmitters serotonin, dopamine, norepinephrine, and epinephrine, as it is the precursor to pyridoxal phosphate, which is the cofactor for the aromatic amino acid decarboxylase enzyme. 

Nevertheless, malonyl-CoA is a major metabolite. It is an intermediate in fatty acid synthesis (see Fig. 17-12) and is formed in the peroxisomal P oxidation of odd chain-length dicarboxylic acids.703 Excess malonyl-CoA is decarboxylated in peroxisomes, and lack of the decarboxylase enzyme in mammals causes the lethal malonic aciduria.703 Some propionyl-CoA may also be metabolized by this pathway. The modified P oxidation sequence indicated on the left side of Fig. 17-3 is used in green plants and in many microorganisms. 3-Hydroxypropionyl-CoA is hydrolyzed to free P-hydroxypropionate, which is then oxidized to malonic semialdehyde and converted to acetyl-CoA by reactions that have not been completely described. Another possible pathway of propionate metabolism is the direct conversion to pyruvate via a oxidation into lactate, a mechanism that may be employed by some bacteria. Another route to lactate is through addition of water to acrylyl-CoA, the product of step a of Fig. 17-3. Tire water molecule adds in the "wrong way," the OH ion going to the a carbon instead of the P (Eq. 17-8). An enzyme with an active site similar to that of histidine ammonia-lyase (Eq. 14-48) could... 

Glucose is converted to pyruvate by the glycolytic pathway (Fig. 5.20). Pyruvate is then oxidised to acetyl-CoA and C02 by the pyruvate decarboxylase enzyme ... 

Biological compounds with long chains of carbon atoms are broken down into molecules with shorter chains by the breaking of carbon-carbon bonds. This commonly occurs by the elimination of -C02H groups from carboxylic acids. For example, pyruvic decarboxylase enzyme acts upon pyruvic acid,... 

A number of decarboxylase enzymes have been described as catalysts for the preparation of chiral synthons, which are difficult to access chemically (see Chapter 2).264 The amino acid decarboxylases catalyze the pyridoxal phosphate (PLP)-dependent removal of C02 from their respective substrates. This reaction has found great industrial utility with one specific enzyme in particular, L-aspartate-P-decarboxylase (E.C. 4.1.1.12) from Pseudomonas dacunhae. This biocatalyst, most often used in immobilized whole cells, has been utilized by Tanabe to synthesize L-alanine on an industrial scale (multi-tons) since the mid-1960s (Scheme 19.33).242-265 Another use for this biocatalyst has been the resolution of racemic aspartic acid to produce L-alanine and D-aspartic acid (Scheme 19.34). The cloning of the L-aspartate-P-decarboxylase from Alcaligenes faecalis into E. coli offers additional potential to produce both of these amino acids.266... 

Second, the decarboxylase enzymes required to produce hydrocarbons apparently are not present in lepidopteran pheromone glands, but these enzymes are present in oenocyte cells where most insect hydrocarbon synthesis takes place (Blomquist et al., 1987). Thus, Lepidoptera that produce Type II pheromones must have a mechanism for transport of hydrocarbon pheromone components from the oenocytes to the pheromone gland, where... 

During fermentation, S. cerevisiae may produce vinylphenol derivatives due to the presence of cinnamate decarboxylase enzymes (Chatonnet et al. 1992, 1993) which are inactive in red juices due to the polyphenol components of red wine (Chatonnet et al. 1997). Several grape juice contamination yeast species also have the ability to form vinylphenols (Dias et al. 2003a) but their contribution to the vinylphenol content of wines may only be relevant when are not inhibited by S. cerevisisiae (Barata et al. 2006). 

In the series of cyclopropane amino acids, compounds 651,652 and 653 have also been studied. The cyclopropyl analogs 651 and 652 showed distinctly lower activity than the corresponding amino acids histidine and thyroxine Compounds 653 were tested for their behavior towards several hydroxylase, aminotransferase and decarboxylase enzyme systems The cis isomer had no inhibitory effect . 

Benkovic and Smiley have reported an orotate decarboxylase antibody obtained by genetic selection starting from a library of antibody genes from an unimmunized animal introduced into abacterial strain lacking orotate decarboxylase enzymes [108]. In essence, bacteria expressing a functional catalytic antibody for the reaction survived and multiplied, and were induced to produce mutations beneficial for catalytic activity. The isolated catalytic antibody is highly active, which brilliantly demonstrates the power of this approach. 

Volatile phenols originate from hydroxycinnamic acids (ferulic, p-coumaric, or caffeic acid) by the action of hydroxycinnamate decarboxylase enzyme, which turn the hydroxycinnamics acid into vinylphe-nols (Albagnac, 1975 Grando et al., 1993). Then, these compounds are reduced to ethyl derivatives by vinylphenol reductase enzymes characteristic of species, such as Dekkera bruxellensis, Dekkera anomala, Pichia guillermondii, Candida versatilis, Candida halophila, and Candida mannitofaciens (Edlin et al., 1995 1998 Dias et al., 2003 Chatonnet et al., 1992 1995 1997 Dias et al., 2003), apart from very small quantities produced by some yeasts and lactic acid bacteria under peculiar growth conditions (Chatonnet et al., 1995 Barata et al., 2006 ... 

During the past few years, there have been developed new antihypertensive agents that might be considered as specific enzyme inhibitors. One of these, a-methyldopa, is an analog of the amino acid 3,4-dihydroxyphenylala-nine. The L-isomer inhibits the decarboxylase enzyme (31) which converts... 

The site of decarboxylation of levodopa in patients with Parkinson s disease is uncertain, but it may be that there is sufficient enzyme in the remaining dopamine nerve terminals or that conversion takes place in other neurons (noradrenergic or serotoniner-gic) as they also contain decarboxylase enzymes. Release of dopamine replaced in this way must be very abnormal but most patients seem to benefit. 

The decarboxylase enzyme shows high enantiomer selectivity reacting only with L-aspartic acid. Thus, L-alanine and D-aspartic acid can be produced from DL-aspartic acid at the same time. 

Sternburg and Kearns (1952) detected the formation of an unknown neuroactive substance in the blood of insects poisoned with DDT. Tashiro et al. (1972) established later that this neuroactive substance is L-leucine. Using L-leucine labelled with they found that, under the action of DDT, the nerve fibre of the insects releases more L-leucine than normal. On the basis of their experimental results they assumed that L-leucine is converted to isoamylamine, the ultimate neurotransmitting agent, by the action of the decarboxylase enzyme (Tashiro et al.,... 

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