Liberation of lipoate by human serum lipoamidase from bovine heart pyruvate dehydrogenase.
Lipoamidase, which hydrolyses such substrates as lipoamide, lipoylmethyl ester, lipoyllysine, and lipoyl 4-aminobenzoate (LPAB), was purified from human serum through use of synthetic substrate LPAB. The purified human serum lipoamidase showed lipoyllysine hydrolase activity (Km = 435 microM, Vmax = 64.5 nmol/min per mg of protein). The purified enzyme did not liberate the free form of lipoic acid from bovine heart pyruvate dehydrogenase (PDH). PDH was hydrolyzed quantitatively by proteinase K to lipoyllysine, which was determined by the HPLC method. Although liberation of lipoate from various lengths of lipoyl-peptides has not been tested yet, it is likely that lipoamidase requires proteinase(s) before the liberation of free lipoic acid from the enzymes.
Oizumi
J
J
National Children's Medical Research Center, Division of Metabolism, Tokyo, Japan.
Hayakawa
K
K
D000581:Amidohydrolases / Q000097:blood*; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D019286:Endopeptidase K; D006801:Humans; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism; D013552:Swine; D008063:Thioctic Acid / Q000378:metabolism*
D011768:Pyruvate Dehydrogenase Complex; D008063:Thioctic Acid; D007655:Ketoglutarate Dehydrogenase Complex; D012697:Serine Endopeptidases; D019286:Endopeptidase K; D000581:Amidohydrolases; C023940:lipoamidase