title: Lipoamidase activity in human serum is due to biotinidase.
abstract: Lipoamidase, as determined by lipoyl-p-aminobenzoic acid (L-pABA) hydrolyzing activity, and biotinidase in human serum have similar pH profiles, molecular weights, thermostabilities, and are similarly inhibited by p-hydroxymercuribenzoate and not inhibited by phenylmethylsulfonylfluoride. A monospecific polyclonal antibody prepared against biotinidase immunoprecipitated greater than 95% of serum L-pABA hydrolyzing activity and an identical proportion of biotinidase activity. In addition, children with profound biotinidase deficiency (less than 10% normal serum activity) have greatly reduced levels of L-pABA hydrolyzing activity in serum (less than 15% of mean normal activity) and obligate heterozygotes have activities intermediate between that of normal and profoundly deficient individuals. These results indicate that most, if not all, of the L-pABA hydrolyzing activity in human serum is due to biotinidase. Moreover, since the Km of L-pABA hydrolysis by serum is high, it is unlikely that lipoic acid is recycled in the serum by biotinidase.
authors.affiliation: Department of Human Genetics, Medical College of Virginia, Richmond 23298.
authors.forename: C L
authors.initials: CL
authors.lastname: Garganta
authors.forename: B
authors.initials: B
authors.lastname: Wolf
mesh_terms: D010129:4-Aminobenzoic Acid / Q000097:blood; D000581:Amidohydrolases / Q000097:blood* / Q000378:metabolism; D062365:Aminobenzoates; D001710:Biotin / Q000031:analogs & derivatives / Q000097:blood; D043523:Biotinidase; D002850:Chromatography, Gel / Q000379:methods; D004795:Enzyme Stability; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D006902:Hydroxymercuribenzoates / Q000494:pharmacology; D007700:Kinetics; D008895:Milk, Human / Q000201:enzymology / Q000378:metabolism; D008970:Molecular Weight; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D008063:Thioctic Acid / Q000031:analogs & derivatives / Q000097:blood; D062366:para-Aminobenzoates
chemical_list: D062365:Aminobenzoates; D006902:Hydroxymercuribenzoates; D062366:para-Aminobenzoates; C066182:lipoyl-4-aminobenzoic acid; C030601:4-hydroxymercuribenzoate; C051399:N-biotinyl-4-aminobenzoic acid; D010664:Phenylmethylsulfonyl Fluoride; D001710:Biotin; D008063:Thioctic Acid; D000581:Amidohydrolases; C023940:lipoamidase; D043523:Biotinidase; D010129:4-Aminobenzoic Acid