Acylase I-Catalyzed Deacetylation of N-Acetyl-l-cysteine and S-Alkyl-N-acetyl-l-cysteines
摘要:
The aminoacylase that catalyzes the hydrolysis of N-acetyl-L-cysteine (NAC) was identified as acylase I after purification by column chromatography and electrophoretic analysis. Rat kidney cytosol was fractionated by ammonium sulfate precipitation, and the proteins were separated by ion-exchange column chromatography, gel-filtration column chromatography, and hydrophobic interaction column chromatography. Acylase activity with NAC and N-acetyl-L-methionine (NAM), a known substrate for acylase I, as substrates coeluted during all chromatographic steps. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the protein was purified to near homogeneity and had a subunit M-r of 43 000, which is identical with the M-r of acylase I from porcine kidney and bovine liver. n-Butylmalonic acid was a slow-binding inhibitor of acylase I and inhibited the deacetylation of NAC with a K-i of 192 +/- 27 mu M These results show that acylase I catalyzes the deacetylation of NAG. The acylase I-catalyzed deacetylation of a range of S-alkyl-N-acetyl-L-cysteines, their carbon and oxygen analogues, and the selenium analogue of NAM was also studied with porcine kidney acylase I. The specific activity of the acylase I-catalyzed deacetylation of these substrates was related to their calculated molar volumes and lag P values. The S-alkyl-N-acetyl-L-cysteines with short (C-0-C-3) and unbranched S-alkyl substituents were good acylase I substrates, whereas the S-alkyl-N-acetyl-L-cysteines with long (>C-3) and branched S-alkyl substituents were poor acylase I substrates. The carbon and oxygen analogues of S-methyl-N-acetyl-L-cysteine and the carbon analogue of S-ethyl-N-acetyl-L-cysteine were poor acylase I substrates, whereas the selenium analogue of NAM was a good acylase I substrate.
The S -alkyl chain length as a determinant of the anti-leukemic activity of cysteine chloromethyl ketone compounds
摘要:
A series of cysteine chloromethyl ketone compounds with a systematic variation of the S-alkyl chain length have been synthesized in order to gauge the effect of the alkyl chain length on the cytotoxicity of these compounds against human acute lymphoblastic leukemia cells. Comparable activities were observed for compounds with S-alkyl chains ranging from pentyl to dodecyl, with the best being undecyl (IC50 = 1.7 mu M) and dodecyl (IC50 = 2.0 mu M) against B-lineage leukemia cells and hexyl (IC50 = 0.7 mu M) against T-lineage leukemia cells. (C) 2000 Elsevier Science Ltd. All rights reserved.