Carboxybiotin translocation mechanisms suggested by diffraction studies of biotin and its vitamers.
AUTOR(ES)
DeTitta, G T
RESUMO
Biotin is a coenzyme that fixes CO2 for transfer in a family of carboxylase, decarboxylase, and transcarboxylase enzymes. Their enzyme reactions involve two basic steps during which a carboxybiotinyl intermediate forms at one site and translocates to a second (distinct) site for CO2 transfer. Our diffraction studies of biotin and its vitamers suggest that translocation involves rotation about one, or at most two, bonds in biotin's valeryl chain. The rotations are energetically economical gauche in equilibrium trans rotations about the two valeryl bonds nearest the biotin bicyclic ring. They move a carbon atom of a CO2 moiety bound at N-1' approximately 7 A, a distance in accord with spectroscopic measurements of one of the biotin enzymes. From our studies we infer that sulfur in biotin imparts to the valeryl chain a conformational variability necessary for bond rotation and, hence, translocation between catalytic sites.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=348264Documentos Relacionados
- Metabolism of Biotin and Analogues of Biotin by Microorganisms1: II. Further Studies on the Conversion of d-Biotin to Biotin Vitamers by Lactobacillus plantarum
- Conversion of d-Biotin to Biotin Vitamers by Lactobacillus arabinosus
- BIOTIN BIOSYNTHESIS I. : Biotin Yields and Biotin Vitamers in Cultures of Phycomyces blakesleeanus
- Repression of Biotin Biosynthesis in Escherichia coli During Growth on Biotin Vitamers
- Demonstration of Two Translocation Mechanisms in Studies of Bidirectional Movement 123
