Biotin metabolism in plants

Biotin is an essential cofactor for a small number of enzymes involved main ly in the transfer of CO2 during HCO3--dependent carboxylation reactions. T his review highlights progress in plant biotin research by focusing on the four major areas of recent investigation: the structure, enzymology, and lo calization of two important biotinylated proteins (methylcrotonoyl-CoA carb oxylase involved in the catabolism of leucine and noncyclic isoprenoids; ac etyl-CoA carboxylase isoforms involved in a number of biosynthetic pathways ); the biosynthesis of biotin; the biotinylation of biotin-dependent carbox ylases, including the characterization of biotin holocarboxylase synthetase isoforms; and the detailed characterization of a novel, seed-specific biot inylated protein. A central challenge for plant biotin research is to deter mine in molecular terms how plant cells regulate the flow of biotin to sust ain the biotinylation of biotin-dependent carboxylases during biosynthetic reactions.