Stefano G B, Salzet-Raveillon B, Salzet M
Multidisciplinary Center for the study of Aging, Neuroscience Research Institute, State University of New York, College at Old Westbury, Old Westbury, NY 11568-0210, USA.
Brain Res Mol Brain Res. 1999 Jan 8;63(2):340-50. doi: 10.1016/s0169-328x(98)00252-6.
Mytilus edulis hemolymph contains mammalian-like proopiomelanocortin (POMC). The 20 kDa protein was purified by high pressure gel permeation chromatography, anti-adrenocorticotropin (ACTH)-affinity column and reverse-phase HPLC. The amino acid sequence determination was by Edman degradation, enzymatic treatments and Western blot analysis. Of the six peptides found in this opioid precursor, methionine-enkephalin, gamma-melanocyte stimulating hormone (MSH), alpha-MSH and ACTH exhibited 100, 80, 85 and 74% sequence identity, respectively, with the mammalian counterparts. beta-Endorphin and gamma-LPH exhibited only 25 and 10% sequence identity. Dibasic amino acid residues were found at the C-terminus of MSH and ACTH, indicating cleavage sites. The alpha-MSH is flanked at the C-terminus by Gly-Lys-Lys, representing an amidation signal. ACTH and CLIP (80% sequence identity) are also C-terminally flanked by dibasic amino acid residues. Furthermore, morphine, in a dose-dependent manner, increased the hemolymph levels of alpha-MSH and ACTH (1-39) in a naloxone and phosphoramidon antagonizable manner, indicating a neutral endopeptidase (24.11; NEP) mediated cleavage. Lipopolysaccharide (10 microg/animal) stimulated the processing of ACTH (1-39) yielding ACTH (1-24) in a cleavage that is independent of NEP, but dependent on aspartyl proteases, demonstrating differential enzymatic cleavage of ACTH (1-39). Taken together, POMC is present in invertebrates and its processing can be altered depending on the signal.
贻贝血淋巴中含有类哺乳动物的阿片促黑激素皮质素原（POMC）。通过高压凝胶渗透色谱、抗促肾上腺皮质激素（ACTH）亲和柱和反相高效液相色谱法纯化了这种20 kDa的蛋白质。通过埃德曼降解法、酶处理和蛋白质免疫印迹分析确定了氨基酸序列。在这种阿片肽前体中发现的六种肽中，甲硫氨酸脑啡肽、γ-促黑素细胞激素（MSH）、α-MSH和ACTH与哺乳动物对应物的序列同一性分别为100%、80%、85%和74%。β-内啡肽和γ-促脂素的序列同一性仅为25%和10%。在MSH和ACTH的C末端发现了双碱性氨基酸残基，表明存在切割位点。α-MSH在C末端两侧是Gly-Lys-Lys，代表酰胺化信号。ACTH和促肾上腺皮质激素样中叶肽（CLIP，序列同一性80%）在C末端也有双碱性氨基酸残基。此外，吗啡以剂量依赖性方式增加了α-MSH和ACTH（1-39）的血淋巴水平，且这种增加可被纳洛酮和磷酰胺拮抗，这表明是一种中性内肽酶（24.11；NEP）介导的切割。脂多糖（10微克/动物）刺激了ACTH（1-39）的加工，产生了ACTH（1-24），这种切割不依赖于NEP，而是依赖于天冬氨酰蛋白酶，这表明ACTH（1-39）存在不同的酶促切割。综上所述，POMC存在于无脊椎动物中，其加工过程可根据信号而改变。
