1,721,003 research outputs found
The steady state kinetics of tyrosine decarboxylase from Streptococcus faecalis.
No full textThe present study has explained the general reaction mechanism of the bacterial tyrosine decarboxylase. The rate equation for this mechanism has been presented. The steady state kinetics of tyrosine decarboxylase, as for tyrosine transaminase, have shown that the apoenzyme can bind not only the coenzyme, but also the non-enzymatically formed Schiff base between the coenzyme and the substrate. Our data then have confirmed the importance of the non-enzymatically formed Schiff base in the B6-dependent enzymes, possibly in all of them which have a low affinity constant for the coenzyme, such that the coenzyme must be present in excess in respect to the protein to saturate the active center. The interaction between apotyrosine decarboxylase with pyridoxal-5'-phosphate and pyridoxamine-5'-phosphate has been studied
Alpha5 pyridoxalacetic acid and alpha5 pyridoxyl-L-phenylalamide acetic acid: their action on same B6-dependent enzymes
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Ornithine and glutamate decarboxylases catalyse an oxidative deamination of their alpha-methyl substrates
No full textOrnithine decarboxylase (ODC) from Lactobacillus 30a catalyses the cleavage of α-methylornithine into ammonia and 2-methyl-1-pyrroline; glutamate decarboxylase (GAD) from Escherichia coli catalyses the cleavage of α-methylglutamate into ammonia and laevulinic acid. In our analyses, 2-methyl-1-pyrroline and laevulinic acid were identified by HPLC and mass spectroscopic analysis, and ammonia was identified by means of glutamate dehydrogenase. Molecular oxygen was consumed during these reactions in a 1:2 molar ratio with respect to the products. The catalytic efficiencies (kcat/Km) of the reactions catalysed by ODC and GAD were determined as 12500 and 9163 M-1 ̇min-1 respectively. When the reactions were performed under anaerobic conditions, no ammonia, 2-methyl-1-pyrroline or laevulinic acid was produced to a significant extent. The formation of ammonia and O2 consumption (in a 1:2 molar ratio with respect to ammonia) were also detected during the reaction of ODC and GAD with putrescine and γ-aminobutyrate respectively. Taken together, these findings clearly indicate that ODC and GAD catalyse an oxidative deamination of their decarboxylation products, a reaction similar to that catalysed by dopa decarboxylase (DDC) with α-methyldopa [Bertoldi, Dominici, Moore, Maras and Borri Voltattorni (1998) Biochemistry 37, 6552-6561]. Furthermore, this reaction was accompanied by a decarboxylation-dependent transamination occurring for GAD, DDC and ODC with a frequency of approx. 0.24%, 1% and 9% respectively compared with that of oxidative deamination.Ornithine decarboxylase (ODC) from Lactobacillus 30a catalyses the cleavage of alpha-methylornithine into ammonia and 2-methyl-1-pyrroline; glutamate decarboxylase (GAD) from Escherichia coli catalyses the cleavage of alpha-methylglutamate into ammonia and laevulinic acid. In our analyses, 2-methyl-1-pyrroline and laevulinic acid were identified by HPLC and mass spectroscopic analysis, and ammonia was identified by means of glutamate dehydrogenase. Molecular oxygen was consumed during these reactions in a 1.2 molar ratio with respect to the products. The catalytic efficiencies (k(cat)/K-m) of the reactions catalysed by ODC and GAD were determined as 12500 and 9163 M-1.min(-1) respectively. When the reactions were performed under anaerobic conditions, no ammonia, 2-methyl-1-pyrroline or laevulinic acid was produced to a significant extent. The formation of ammonia and O-2 consumption (in a 1:2 molar ratio with respect to ammonia) were also detected during the reaction of ODC and GAD with putrescine and gamma-aminobutyrate respectively. Taken together, these findings clearly indicate that ODC and GAD catalyse an oxidative deamination of their decarboxylation products. a reaction similar to that catalysed by dopa decarboxylase (DDC) with alpha-methyldopa [Bertoldi, Dominici, Moore, Maras and Borri Voltattorni (1998) Biochemistry 37, 6552-6561]. Furthermore, this reaction was accompanied by a decarboxylation-dependent transamination occurring for GAD, DDC and ODC with a frequency of approx. 0.24%, 1% and 9% respectively compared with that of oxidative deamination
MODIFIED PURIFICATION OF L-AROMATIC AMINO-ACID DECARBOXYLASE FROM PIG KIDNEY
No full textMODIFIED PURIFICATION OF DOPA DECARBOXYLASE FROM PIG KIDNE
Interaction of N-(DL-seryl)N'-(2,3,4-trihydroxybenzyl)-hydrazine with L-dopa decarboxylase from pig kidney.
No full textChemical modification of pig kidney 3,4-dihydroxyphenylalanine decarboxylase with diethyl pyrocarbonate. Evidence for an essential histidyl residue.
No full textInteraction of L-alpha-methyl-alpha-hydrazino-3,4 dihydroxyphenylpropionic acid with dopa-decarboxylase from pig kidney.
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