von Zastrow M, Tritton T R, Castle J D
Proc Natl Acad Sci U S A. 1986 May;83(10):3297-301. doi: 10.1073/pnas.83.10.3297.
Exocrine secretion granules from the rat parotid gland contain a carboxyl-terminal peptide alpha-amidation enzyme resembling closely an enzyme from the pituitary (peptidyl-glycine alpha-amidating monooxygenase) that functions in post-translational processing of secretory polypeptides within neural and endocrine secretion granules. alpha-Amidation is a characteristic (often essential) chemical feature of a variety of biologically active regulatory peptides in animals. The parotid and pituitary activities exhibit very similar ascorbate and copper requirements, pH dependence, and kinetic properties. Further, like the pituitary enzyme(s), the parotid activity is found predominantly in secretion granule content and is discharged by exocytosis. These results establish the presence of a novel enzyme in exocrine secretion granules and suggest a potential role of the L-ascorbic acid contained in parotid granules. Two additional findings--the detection of similar levels of amidation activity in purified secretion granule fractions from other exocrine glands and the observation, in parotid granule fractions, of a B-type carboxypeptidase activity similar to that involved in post-translational processing in other systems--form a rational basis for considering whether exocrine secretion granules (like their neural and endocrine counterparts) serve as post-translational processing sites. The identity and functional role of the modified polypeptides remain to be determined.
大鼠腮腺的外分泌分泌颗粒含有一种羧基末端肽α-酰胺化酶，它与垂体中的一种酶（肽基甘氨酸α-酰胺化单加氧酶）非常相似，该酶在神经和内分泌分泌颗粒内的分泌多肽的翻译后加工中起作用。α-酰胺化是动物体内多种生物活性调节肽的一个特征性（通常是必需的）化学特性。腮腺和垂体的活性表现出非常相似的抗坏血酸和铜需求、pH依赖性和动力学特性。此外，与垂体酶一样，腮腺的活性主要存在于分泌颗粒内容物中，并通过胞吐作用释放。这些结果证实了外分泌分泌颗粒中存在一种新型酶，并提示了腮腺颗粒中所含L-抗坏血酸的潜在作用。另外两个发现——在来自其他外分泌腺的纯化分泌颗粒组分中检测到相似水平的酰胺化活性，以及在腮腺颗粒组分中观察到一种与其他系统中参与翻译后加工的B型羧肽酶活性相似的活性——为考虑外分泌分泌颗粒（如同它们的神经和内分泌对应物）是否作为翻译后加工位点提供了合理依据。修饰多肽的身份和功能作用仍有待确定。
