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Title: Studies on biotin dependent carboxylases and the properties of carboxybiotin

Abstract

Biotin dependent carboxyl-transfer reactions have been studied using biotin and pyruvate carboxylases. The pH profile for the Mg/sup 2 +/ and MgATP dependent carboxylation of biotin by bicarbonate shows that an enzymic base with a pK of 6.5 must be unprotonated for catalysis to occur. The pH profiles for the carboxyl-transfer reaction of pyruvate carboxylase have been obtained by studying the decarboxylation of oxalacetate stimulated by the presence of oxamate. Similarly, /sup 13/C and /sup 2/H isotope effects have been measured for the decarboxylation of oxalacetate by both enzymic and nonenzymic means. From these studies the authors can conclude that carboxyl-transfer between biotin and oxalacetate is at least partially rate-limiting and is not concerted with proton-transfer. The lack of any apparent enzymic acid-base catalyst (the V/K profile for oxalacetate is pH independent) suggests that proton transfer may occur directly between biotin and the carbanion formed when oxalacetate is decarboxylated. The pH profile for the nonenzymatic decarboxylation of carboxybiotin shows a plateau below pH 4 (k = 0.012 min/sup -1/ at 2/sup 0/C), and a lower plateau above pH 8 (k = 0.005 min/sup -1/ at 25/sup 0/C). A proton inventory at low pH is linear, while at high pH itmore » is curved. These data suggest that two different mechanisms operate at high and low pH.« less

Authors:
; ;
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison
OSTI Identifier:
5220373
Report Number(s):
CONF-8606151-
Journal ID: CODEN: FEPRA
Resource Type:
Conference
Journal Name:
Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
Additional Journal Information:
Journal Volume: 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; BIOTIN; CARBOXYLATION; CARBON 13; ISOTOPE EFFECTS; CARBOXYLASE; BIOCHEMICAL REACTION KINETICS; DEUTERIUM; CATALYSIS; CHEMICAL PROPERTIES; DECARBOXYLATION; OXALATES; PH VALUE; PROTONS; AZOLES; BARYONS; CARBON ISOTOPES; CARBON-CARBON LYASES; CARBOXY-LYASES; CARBOXYLIC ACID SALTS; CARBOXYLIC ACIDS; CHEMICAL REACTIONS; ELEMENTARY PARTICLES; ENZYMES; EVEN-ODD NUCLEI; FERMIONS; HADRONS; HETEROCYCLIC ACIDS; HETEROCYCLIC COMPOUNDS; HYDROGEN ISOTOPES; IMIDAZOLES; ISOTOPES; KINETICS; LIGHT NUCLEI; LYASES; NUCLEI; NUCLEONS; ODD-ODD NUCLEI; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANIC SULFUR COMPOUNDS; REACTION KINETICS; STABLE ISOTOPES; VITAMIN B GROUP; VITAMINS; 550201* - Biochemistry- Tracer Techniques

Citation Formats

Tipton, P A, Attwood, P V, and Cleland, W W. Studies on biotin dependent carboxylases and the properties of carboxybiotin. United States: N. p., 1986. Web.
Tipton, P A, Attwood, P V, & Cleland, W W. Studies on biotin dependent carboxylases and the properties of carboxybiotin. United States.
Tipton, P A, Attwood, P V, and Cleland, W W. Thu . "Studies on biotin dependent carboxylases and the properties of carboxybiotin". United States.
@article{osti_5220373,
title = {Studies on biotin dependent carboxylases and the properties of carboxybiotin},
author = {Tipton, P A and Attwood, P V and Cleland, W W},
abstractNote = {Biotin dependent carboxyl-transfer reactions have been studied using biotin and pyruvate carboxylases. The pH profile for the Mg/sup 2 +/ and MgATP dependent carboxylation of biotin by bicarbonate shows that an enzymic base with a pK of 6.5 must be unprotonated for catalysis to occur. The pH profiles for the carboxyl-transfer reaction of pyruvate carboxylase have been obtained by studying the decarboxylation of oxalacetate stimulated by the presence of oxamate. Similarly, /sup 13/C and /sup 2/H isotope effects have been measured for the decarboxylation of oxalacetate by both enzymic and nonenzymic means. From these studies the authors can conclude that carboxyl-transfer between biotin and oxalacetate is at least partially rate-limiting and is not concerted with proton-transfer. The lack of any apparent enzymic acid-base catalyst (the V/K profile for oxalacetate is pH independent) suggests that proton transfer may occur directly between biotin and the carbanion formed when oxalacetate is decarboxylated. The pH profile for the nonenzymatic decarboxylation of carboxybiotin shows a plateau below pH 4 (k = 0.012 min/sup -1/ at 2/sup 0/C), and a lower plateau above pH 8 (k = 0.005 min/sup -1/ at 25/sup 0/C). A proton inventory at low pH is linear, while at high pH it is curved. These data suggest that two different mechanisms operate at high and low pH.},
doi = {},
url = {https://www.osti.gov/biblio/5220373}, journal = {Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)},
number = ,
volume = 45:6,
place = {United States},
year = {1986},
month = {5}
}

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