Aminopeptidase C of Aspergillus niger Is a Novel Phenylalanine Aminopeptidase

A novel enzyme with a specific phenylalanine aminopeptidase activity (ApsC) from Aspergillus niger (CBS 120.49) has been characterized. The derived amino acid sequence is not similar to any previously characterized aminopeptidase sequence but does share similarity with some mammalian acyl-peptide hydrolase sequences. ApsC was found to be most active towards phenylalanine β-naphthylamide (F-βNA) and phenylalanine para-nitroanilide (F-pNA), but it also displayed activity towards other amino acids with aromatic side chains coupled to βNA; other amino acids with nonaromatic side chains coupled to either pNA or βNA were not hydrolyzed or were poorly hydrolyzed. ApsC was not able to hydrolyze N-acetylalanine-pNA, a substrate for acyl-peptide hydrolases.本研究对源自黑曲霉（Aspergillus niger，菌株编号CBS 120.49）的新型酶ApsC——其具有特异性苯丙氨酸氨肽酶活性——完成了系统表征。该酶的推导氨基酸序列与所有已报道的已表征氨肽酶序列均无同源性，但与部分哺乳动物酰基肽水解酶序列存在一定的序列相似性。实验结果表明，ApsC对苯丙氨酸β-萘酰胺（F-βNA）和苯丙氨酸对硝基苯胺（F-pNA）的催化活性最高，同时对其他带有芳香侧链且与βNA偶联的氨基酸也表现出水解活性；而对于带有非芳香侧链且与pNA或βNA偶联的氨基酸，ApsC均无法实现水解，仅能发生极微弱的水解反应。此外，ApsC无法水解酰基肽水解酶的经典底物N-乙酰丙氨酸-pNA。