Parathyroid Hormone-Action and Degradation
Peptide hormone hydrolysis has two main purposes. One is processing, and the other is degradation. In most of the hormones, these two processes are clearly distinguished, because the former takes place in the secretory gland and the latter in the target organ. The former is a metabolically controlled limited hydrolysis yielding certain active fragment, whereas the latter is a random hydrolysis to generate small, in-active fragments with no other purpose but getting rid of the biological effect of the hormone. While the processing and generation of active fragment is directly connected with the action of the hormone, degradation into small fragments may be involved only indirectly in the control of hormone action, by controlling its rate of disappearance and consequently, the half-life of the hormone in blood. Parathyroid hormone is unique in its inhibition of secretion by calcium ion along with renin, and this was explained by calcium stimulation of its degradation already in the secretory gland, from which only inactive fragments are secreted during hypercalcemia, because of the augmentation of PTH degradation in the parathyroid glands. It is thus difficult to separate processing and degradation of PTH. In the target cells of PTH, both processing and degradation may take place.
KeywordsHydrolysis Glutathione Cystein Serine Trypsin
Unable to display preview. Download preview PDF.
- 1.T. Fujita, M. Ohata, M. Yoshikawa, M. Maruyama, Enzymatic hydrolysis of 125I-labeled Parathyroid Hormone, Endocrinol. Japan. 16: 383 (1969)Google Scholar
- 2.T. Fujita, H. Baba, M. Sase, M. Fukushima, Y. Nishii, Parathyroid hormone-degrading enzyme of high molecular weight in the cytosol of rat renal cortical cells, Bone & Mineral, 1: 457 (1986).Google Scholar
- 3.T. Fujita, H. Baba, Y. Yoshimoto, M. Fukase, M. Kishihawa, M. Tomon, T. Fukami, Y. Imai, Y. Nishii, M. Fukushima, Physiological significance of PTH degradation through limited hydrolysis by rat kidney cytosolic enzymes,Endocrine Control of Bone & Calcium Metabolism Ed. D.V. Cohn, T. Fujita, J.T. Potts, Jr., Elsevier p 238 (1984).Google Scholar
- 4.T. Yamaguchi, H. Baba, M. Fukase, Y. Kinoshita, T. Fujimoto, T. Fujita, Degrading activity for human parathyroid hormone (hPTH 1–84) in rat osteoblast-like osteosarcoma cell line UMR 106, Biochem. Biophys. Research Comm. 141: 762 (1986).Google Scholar
- T. Yamaguchi, H. Baba, M. Fukase, Y. Kinoshita, T. Fujimi, T. Fujita, Possible involvement of protein kinase C in parathyroid hormone de-gradation by osteoblast-like rat osteosarcoma cell line UMR-106.Google Scholar