Eipper B A, Myers A C, Mains R E
Endocrinology. 1985 Jun;116(6):2497-504. doi: 10.1210/endo-116-6-2497.
Bioactive peptides frequently terminate in a carboxyl-terminal alpha-amide. The tissue distribution of enzymatic activity capable of converting [125I]D-Tyr-Val-Gly into [125I]D-Tyr-Val-NH2 has been determined. Assay conditions have been established so that enzyme activity can be measured in crude homogenates. In adult male rats, the highest concentrations of activity are found in the anterior and neurointermediate lobes of the pituitary. Lower concentrations of activity are found in the hypothalamus, submandibular glands, and the rest of the brain. Enzyme activity is also easily assayed in serum. Taking into account the mass of each tissue, the submandibular glands and the brain are the major tissue sources of enzymatic activity; serum contains more enzymatic activity than is found in the pituitary gland. In all tissues and in serum, enzyme activity is stimulated by the addition of copper sulfate and ascorbate and is dependent on molecular oxygen. This activity is, therefore, referred to as peptidyl glycine alpha-amidating monooxygenase (PAM) activity. The pH optima for PAM activity in the pituitary and submandibular glands are near neutrality, whereas the pH optima for PAM activity in serum and hypothalamus are broad, with substantial activity at alkaline pH.
生物活性肽通常在羧基末端以α-酰胺形式终止。已经确定了能够将[125I]D-酪氨酸-缬氨酸-甘氨酸转化为[125I]D-酪氨酸-缬氨酸-NH2的酶活性的组织分布。已经建立了测定条件，以便能够在粗匀浆中测量酶活性。在成年雄性大鼠中，垂体前叶和神经中间叶中的活性浓度最高。下丘脑、下颌下腺和大脑其他部位的活性浓度较低。血清中也很容易检测到酶活性。考虑到每个组织的质量，下颌下腺和大脑是酶活性的主要组织来源；血清中含有的酶活性比垂体中的更多。在所有组织和血清中，添加硫酸铜和抗坏血酸盐可刺激酶活性，且酶活性依赖于分子氧。因此，这种活性被称为肽基甘氨酸α-酰胺化单加氧酶（PAM）活性。垂体和下颌下腺中PAM活性的最适pH接近中性，而血清和下丘脑中PAM活性的最适pH范围较宽，在碱性pH下有大量活性。
