A succinyl-trialanine p-nitroanilide hydrolase in hog kidney cytosol: Its identification as proline endopeptidase.
作者:SHINJI SOEDA、MASANORI OHYAMA、ATSUO NAGAMATSU
DOI:10.1248/cpb.32.1510
日期:——
A succinyl-trialanine p-nitroanilide [Suc-(Ala)3-pNA] hydrolase which is able to hydrolyze an artificial elastase substrate, Suc-(Ala)3-pNA, but unable to hydrolyze a naturally occurring substrate, elastin, was highly purified from hog kidney cytosol. The apparent molecular weight of the enzyme was estimated to be 65000 by gel filtration on Sephadex G-150 and 68000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the isoelectric point of the enzyme was 5.0. The enzyme is an endopeptidase which catalyzes the hydrolysis of peptides with the general structure Y-Ala (or Pro)-X (Y=peptide or N-protected amino acid ; X=amino acid moiety, peptide or amide) at the carboxyl side of alanine and proline residues. The enzyme was markedly inhibited by diisopropyl fluorophosphate and p-chloromercuribenzoate. Ethylenediaminetetraacetate and 1, 10-phenanthroline, however, were not inhibitors of the enzyme. The enzyme activity was retained on an affinity column having a proline endopeptidase [EC 3.4.21.26] inhibitor, Z-Gly-Pro, as ligand and could be eluted at 0.125M NaCl (mean value). Suc-(Ala)3-pNA-hydrolytic activity coincided with the peak of proline endopeptidase activity as determined with a sensitive fluorogenic substrate, succinylglycyl-L-proline 4-methylcoumaryl-7-amide (Suc-Gly-Pro-MCA). The optimum pH and kcat/Km values (mM-1·s-1) were pH 7.5 and 5.4 for Suc-(Ala)3-pNA and pH 6.8 and 24.8 for Suc-Gly-Pro-MCA, and the enzyme activity was competitively inhibited by Z-Ala-Ala and Z-Gly-Pro, as is the case with proline endopeptidase. These results suggest that Suc-(Ala)3-pNA hydrolase in hog kidney cytosol may be identical with proline endopeptidase which was first found in human uterus as an oxytocindegrading enzyme.
从猪肾细胞液中高度纯化了一种琥珀酰-鸟嘌呤对硝基苯胺[Suc-(Ala)3-pNA]水解酶,该酶能够水解人工弹性蛋白酶底物 Suc-(Ala)3-pNA,但不能水解天然底物弹性蛋白。通过在 Sephadex G-150 上进行凝胶过滤,估计该酶的表观分子量为 65000,通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳,估计该酶的表观分子量为 68000,等电点为 5.0。该酶是一种内肽酶,可催化水解一般结构为 Y-Ala(或 Pro)-X(Y=肽或 N-保护氨基酸;X=氨基酸分子、肽或酰胺)的肽,其结构位于丙氨酸和脯氨酸残基的羧基侧。氟磷酸二异丙酯和对氯脲苯甲酸酯对该酶有明显的抑制作用。然而,乙二胺四乙酸盐和 1,10-菲罗啉不是该酶的抑制剂。以脯氨酸内肽酶[EC 3.4.21.26] 抑制剂 Z-Gly-Pro 为配体的亲和柱可保留酶的活性,并可在 0.125M NaCl(平均值)条件下洗脱。蔗糖-(Ala)3-pNA-水解活性与脯氨酸内肽酶活性的峰值相吻合,脯氨酸内肽酶活性是用敏感的荧光底物琥珀酰甘氨酰-L-脯氨酸 4-甲基香豆素-7-酰胺(Suc-Gly-Pro-MCA)测定的。Suc-(Ala)3-pNA 的最适 pH 值和 kcat/Km 值(mM-1-s-1)分别为 pH 7.5 和 5.4,Suc-Gly-Pro-MCA 的最适 pH 值和 kcat/Km 值(mM-1-s-1)分别为 pH 6.8 和 24.8。这些结果表明,猪肾细胞质中的 Suc-(Ala)3-pNA 水解酶可能与脯氨酸内肽酶相同。