DeLapp N W, Dieckman D K
Elizabeth Arden Research, Eli Lilly and Company, Indianapolis, Indiana 46285.
J Invest Dermatol. 1988 Apr;90(4):490-4. doi: 10.1111/1523-1747.ep12460964.
Recent literature has suggested that pyroglutamate (PCA) formation in stratum corneum occurs by spontaneous cyclization of glutamine residues derived from filaggrin breakdown. This paper describes an enzymatic alternative. Epidermal homogenates from hairless mice were found to catalyze the formation of PCA from both glutamine and glutamic acid at pH 6.2. Enzyme activity responsible for the first step in this reaction, gamma-glutamyl peptide formation, was partially purified using ammonium sulfate precipitation followed by ion exchange, gel filtration, and hydroxylapatite chromatography. Enzyme preparations free of gamma-glutamyl cyclotransferase activity (which forms PCA from certain gamma-glutamyl peptides) catalyzed formation of gamma-glutamyl-glutamine from glutamine and gamma-glutamyl-glutamate from glutamic acid. Enzyme preparations catalyzed hydrolysis of a variety of gamma-glutamyl peptides but did not split non-gamma-glutamyl peptides or the transpeptidase substrate gamma-glutamyl-rho-nitroanilide. Ammonium sulfate fractions containing both gamma-glutamyl peptidase and gamma-glutamyl cyclotransferase activity catalyzed linear formation of PCA from glutamic acid for periods of up to 19 h. Using gamma-glutamyl-leucine as a substrate, gamma-glutamyl peptidase activity was found to be much higher in crude extracts from epidermis than in preparations from liver, kidney, spleen, intestine, lung, brain, or heart. This activity has not, to our knowledge, been previously described in mammalian tissues.
近期文献表明，角质层中焦谷氨酸（PCA）的形成是由丝聚合蛋白分解产生的谷氨酰胺残基自发环化所致。本文描述了一种酶促替代途径。研究发现，无毛小鼠的表皮匀浆在pH 6.2时可催化谷氨酰胺和谷氨酸生成PCA。负责该反应第一步即γ-谷氨酰肽形成的酶活性，通过硫酸铵沉淀，随后进行离子交换、凝胶过滤和羟基磷灰石色谱进行部分纯化。不含γ-谷氨酰环转移酶活性（由某些γ-谷氨酰肽形成PCA）的酶制剂可催化谷氨酰胺生成γ-谷氨酰-谷氨酰胺，谷氨酸生成γ-谷氨酰-谷氨酸。酶制剂可催化多种γ-谷氨酰肽的水解，但不会裂解非γ-谷氨酰肽或转肽酶底物γ-谷氨酰-对硝基苯胺。同时含有γ-谷氨酰肽酶和γ-谷氨酰环转移酶活性的硫酸铵级分可催化谷氨酸线性生成PCA，长达19小时。以γ-谷氨酰-亮氨酸为底物时，发现表皮粗提物中的γ-谷氨酰肽酶活性远高于肝脏、肾脏、脾脏、肠道、肺、脑或心脏的制剂。据我们所知，这种活性此前在哺乳动物组织中尚未有过描述。
