Isotope effect studies of the pyruvate-dependent histidine decarboxylase from Lactobacillus 30a

Journal Article · Tue Aug 09 04:00:00 EDT 1988 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00416a017· OSTI ID:6823030

Abell, L M; O'Leary, M H

The decarboxylation of histidine by the pyruvate-dependent histidine decarboxylase of Lactobacillus 30 a shows a carbon isotope effect k/sup 12//k/sup 13/ = 1.0334 +/- 0.0005 and a nitrogen isotope effect k/sup 14//k/sup 15/ = 0.9799 +/- 0.0006 at pH 4.8, 37/sup 0/C. The carbon isotope effect is slightly increased by deuteriation of the substrate and slightly decreased in D/sub 2/O. The observed nitrogen isotope effect indicates that the imine nitrogen in the substrate-Schiff base intermediate complex is ordinarily protonated, and the pH dependence of the carbon isotope effect indicates that both protonated and unprotonated forms of this intermediate are capable of undergoing decarboxylation. As with the pyridoxal 5'-phosphate dependent enzyme, Schiff base formation and decarboxylation are jointly rate-limiting, with the intermediate histidine-pyruvate Schiff base showing a decarboxylation/Schiff base hydrolysis ratio of 0.5-1.0 at pH 4.8. The decarboxylation transition state is more reactant-like for the pyruvate-dependent enzyme than for the pyridoxal 5'-phosphate dependent enzyme. These studies find no particular energetic or catalytic advantage to the use of pyridoxal 5'-phosphate over covalently bound pyruvate in catalysis of the decarboxylation of histidine.

• Research Organization: Univ. of Wisconsin, Madison (USA)
• OSTI ID: 6823030
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 27:16; ISSN BICHA
• Country of Publication: United States
• Language: English

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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINO ACIDS
AZOLES
BACTERIA
BIOCHEMICAL REACTION KINETICS
CARBON 12
CARBON 13
CARBON ISOTOPES
CARBON-CARBON LYASES
CARBOXY-LYASES
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECARBOXYLASES
DECARBOXYLATION
DEUTERATION
DEUTERIUM COMPOUNDS
ENZYMES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
HYDROGEN COMPOUNDS
IMIDAZOLES
ISOTOPE EFFECTS
ISOTOPES
KETO ACIDS
KINETICS
LACTOBACILLUS
LIGHT NUCLEI
LYASES
MICROORGANISMS
NITROGEN 14
NITROGEN 15
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
PYRUVIC ACID
REACTION KINETICS
STABLE ISOTOPES
SUBSTRATES