Effects of single nucleotide polymorphisms in the human holocarboxylase synthetase gene on catalytic activity

Holocarboxylase synthetase (HCS) catalyzes the covalent binding of biotin to carboxylases and histones in eukaryotic cells. Biotinylated carboxylases play essential roles in intermediary metabolism; biotinylated histones play essential roles in gene regulation and genome stability. HCS knockout is embryonic lethal. Greater than 1,900 single nucleotide polymorphisms (SNPs) have been reported for HCS, but the biological importance of these polymorphisms is unknown. We hypothesized that some of these SNPs impair catalytic activity and that this effect can be overcome by dietary intervention with biotin. We are currently studying the biotin‐protein ligase activities of eight recombinant HCS morphs using a propionyl‐CoA carboxylase surrogate (“p67”), histone H3, and synthetic histone‐based peptides as substrates for biotinylation. The biotinylation of p67 by T647G HCS and G1528A HCS decreased by ~50% compared with wild‐type HCS. Enzyme kinetic analyses and intervention studies are underway. This is the first biochemical characterization of catalytic activities of HCS morphs. Grant Funding Source : UNL ARD, NIH grants DK063945, DK077816, DK082476 and ES015206