title: Purification and characterization of an amidohydrolase for N4-long-chain fatty acyl derivatives of 1-beta-D-arabinofuranosylcytosine from mouse liver microsomes.
abstract: N4-Long-chain fatty acyl-1-beta-D-arabinofuranosylcytosine amidohydrolase, a metabolizing enzyme for N4-acyl derivatives of 1-beta-D-arabinofuranosylcytosine with long-chain fatty acids, was purified from mouse liver microsomes. The purification was accomplished by solubilization of liver microsomes with Triton X-100, diethylaminoethyl cellulose chromatography, gel filtrations, hydroxyapatite chromatography, and concanavalin A:Sepharose chromatography. On sodium dodecyl sulfate:polyacrylamide gel electrophoresis, the purified enzyme preparation produced a single protein band with a molecular weight of 54,000. The enzyme had an optimal pH of 9.0, and the Michaelis constant for N4-palmitoyl-1-beta-D-arabinofuranosylcytosine was 67 microM. The thiols such as dithiothreitol or 2-mercaptoethanol stabilized the enzyme and stimulated its activity. p-Chloromercuribenzoate, N-ethylmaleimide, diisopropylfluorophosphate, and phenylmethylsulfonyl fluoride strongly inhibited the reaction. Bovine serum albumin markedly stimulated the enzyme activity, whereas detergents such as Triton X-100, deoxycholate, and sodium dodecyl sulfate had little effect. The enzyme did not require monovalent or divalent cations. Among the series of N4-acyl derivatives of 1-beta-D-arabinofuranosylcytosine with different chain lengths of acyl residues, the purified enzyme preferentially hydrolyzed the derivatives with long-chain fatty acids (C12 to C18), and N4-palmitoyl-1-beta-D-arabinofuranosylcytosine was the most susceptible. The purified enzyme was inactive on various N-acylamino acids, amides, oligopeptides, proteins, N-acylsphingosines (ceramides), triglyceride, lecithin, and lysolecithin. These results suggest that N4-long-chain fatty acyl-1-beta-D-arabinofuranosylcytosine amidohydrolase may be a new type of linear amidase.
mesh_terms: D000581:Amidohydrolases / Q000032:analysis / Q000302:isolation & purification* / Q000378:metabolism; D000818:Animals; D003561:Cytarabine / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008862:Microsomes, Liver / Q000201:enzymology*; D008970:Molecular Weight; D011480:Protease Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000494:pharmacology
chemical_list: D011480:Protease Inhibitors; D013438:Sulfhydryl Compounds; D003561:Cytarabine; C047643:N(4)-palmitoyl cytarabine; D000581:Amidohydrolases; C040443:N4-long-chain fatty acyl-arabinofuranosylcytosine amidohydrolase