Katopodis A G, May S W
School of Chemistry, Georgia Institute of Technology, Atlanta 30332.
Biochem Biophys Res Commun. 1988 Feb 29;151(1):499-505. doi: 10.1016/0006-291x(88)90621-3.
Carboxyl terminal alpha-amidation is a prevalent post translational modification in neuropeptide hormones, with amidation being essential for biological activity. We report a direct demonstration and characterization of peptidyl alpha-amidating monooxygenase (PAM) activity in chromaffin granules, secretory vesicles long known as loci for synthesis and storage of catecholamines but only recently recognized as processing and storage sites for neuropeptides. This finding, together with the recently recognized competence of dopamine-b-monooxygenase to carry out N-dealkylation, provides important information regarding the co-localization and co-secretion of multiple neuromodulators. In addition, we introduce a new substrate for both pituitary and chromaffin granule PAM--TNP-D-Tyr-Val-Gly. This substrate exhibits high turnover, and has the important advantage of allowing quantitative activity determinations using standard spectrophotometric techniques, thus facilitating mechanistic studies and inhibitor development.
羧基末端α-酰胺化是神经肽激素中普遍存在的一种翻译后修饰，酰胺化对于生物活性至关重要。我们报告了嗜铬颗粒中肽基α-酰胺化单加氧酶（PAM）活性的直接证明和表征，分泌囊泡长期以来被认为是儿茶酚胺合成和储存的场所，但直到最近才被确认为神经肽的加工和储存位点。这一发现，连同最近认识到的多巴胺-β-单加氧酶进行N-脱烷基化的能力，提供了有关多种神经调节剂共定位和共分泌的重要信息。此外，我们为垂体和嗜铬颗粒PAM引入了一种新底物——TNP-D-酪氨酸-缬氨酸-甘氨酸。该底物具有高周转率，并且具有允许使用标准分光光度技术进行定量活性测定的重要优势，从而便于进行机制研究和抑制剂开发。
