Baumann G
J Clin Endocrinol Metab. 1979 Oct;49(4):495-9. doi: 10.1210/jcem-49-4-495.
The charge isomers of human GH (/GH), isohormones C, D, and E, which result from limited proteolytic cleavage exhibit enhanced biological activity in the rat and in man compared to the intact polypeptide and most abundant form, isohormone B. The mechanism leading to enhanced activity is unknown. To examine the possibility that different in vivo metabolism may represent one such mechanism, the MCRs of radioiodinated hGH-B, -C, and -D were measured in seven normal adults. Significant differences in metabolic clearance were found between isohormones (hGH-B, 108.4; hGH-C, 67.9; hGH-D, 55.7 liters/m2-day). It is concluded that in man, the enzymatically cleaved hGH isohormones are cleared more slowly than hGH-B. Slower metabolism may be a factor responsible for the enhanced biological activity of proteolytically cleaved hGH isohormones.
人生长激素（hGH）的电荷异构体，即等激素C、D和E，是有限蛋白水解裂解的产物，与完整多肽及最丰富的形式等激素B相比，在大鼠和人体内表现出增强的生物活性。导致活性增强的机制尚不清楚。为了研究不同的体内代谢可能是一种机制的可能性，在7名正常成年人中测量了放射性碘化的hGH-B、-C和-D的代谢清除率（MCR）。发现等激素之间的代谢清除存在显著差异（hGH-B为108.4；hGH-C为67.9；hGH-D为55.7升/平方米·天）。得出的结论是，在人体内，酶促裂解的hGH等激素的清除速度比hGH-B慢。代谢较慢可能是蛋白水解裂解的hGH等激素生物活性增强的一个原因。
