Holst J J, Bersani M, Johnsen A H, Kofod H, Hartmann B, Orskov C
Department of Medical Physiology, Panum Institute, Copenhagen, Denmark.
J Biol Chem. 1994 Jul 22;269(29):18827-33.
In the pancreas proglucagon (PG), a peptide precursor of 160 amino acids is cleaved to produce glucagon and a 30-amino acid N-terminal flanking peptide, but the fate of the C-terminal flanking peptide (99 amino acids) is incompletely known. We subjected acid ethanol extracts of human and porcine pancreases to gel filtration and analyzed the fractions with specific radioimmunoassays for the following regions of proglucagon: PG 62-69, PG 72-81, PG 78-87, PG 98-107 amide, PG 126-134, and PG 149-158. Based on these assays and successive purifications by high performance liquid chromatography we isolated and purified to homogeneity three porcine peptides which were subjected to mass spectrometry and sequencing. One peptide was PG 64-69. The second was PG 72-108, as determined by mass spectrometry, N-terminal amino acid sequencing, and specific radioimmunoassays. The third had a molecular size of approximately 10,000, an N-terminal sequence corresponding to PG 72-81, and a C-terminal sequence terminating at PG 158 (specific radioimmunoassay). A similar peptide with an identical N-terminal sequence, a C-terminal sequence corresponding to PG 146-158, and a molecular mass of 9969 (theoretical mass for human PG 72-158 = 9971) was isolated from human pancreas together with small amounts of a peptide corresponding to PG 72-107 amide. Thus, the pancreatic processing of the C-terminal flanking peptide in proglucagon includes the formation of equimolar (to glucagon) amounts of PG 64-69 and PG 72-158 (major proglucagon fragment) and smaller amounts of N-terminally extended glucagon-like peptide-1 (GLP-1) (PG 72-108 in pigs and PG 72-107 amide in humans).
在胰腺中，160个氨基酸的胰高血糖素原（PG）被切割产生胰高血糖素和一个30个氨基酸的N端侧翼肽，但C端侧翼肽（99个氨基酸）的去向尚不完全清楚。我们对人和猪胰腺的酸性乙醇提取物进行凝胶过滤，并用特异性放射免疫分析法分析以下胰高血糖素原区域的组分：PG 62 - 69、PG 72 - 81、PG 78 - 87、PG 98 - 107酰胺、PG 126 - 134和PG 149 - 158。基于这些分析以及通过高效液相色谱进行的连续纯化，我们分离并纯化出三种猪肽至同质状态，对其进行质谱分析和测序。一种肽是PG 64 - 69。第二种经质谱分析、N端氨基酸测序和特异性放射免疫分析法确定为PG 72 - 108。第三种的分子大小约为10,000，N端序列对应于PG 72 - 81，C端序列终止于PG 158（特异性放射免疫分析法）。从人胰腺中分离出一种类似的肽，其N端序列相同，C端序列对应于PG 146 - 158，分子量为9969（人PG 72 - 158的理论分子量 = 9971），同时还含有少量对应于PG 72 - 107酰胺的肽。因此，胰高血糖素原中C端侧翼肽的胰腺加工过程包括形成等摩尔量（与胰高血糖素）的PG 64 - 69和PG 72 - 158（主要的胰高血糖素原片段）以及较少量的N端延伸的胰高血糖素样肽 - 1（GLP - 1）（猪中的PG 72 - 108和人中的PG 72 - 107酰胺）。
