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Endocrinology, doi:10.1210/endo-103-5-1534
Endocrinology Vol. 103, No. 5 1534-1540
Copyright © 1978 by the Endocrine Society.
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Phosphodiesterase and Its Ca2+-Dependent Activating Factor in Bovine Thyroid*

TOSHIHIRO YAGURA, YOSHIE AZUMA, YOSHIHARU AKAZAWA, ITARU NAGATA and HARUTO UCHINO

The First Division, Department of Internal Medicine, Kyoto University School of Medicine (H.U.) Kyoto
Division of Internal Medicine Kyoto National Hospital (Y.A., Y.A.),Kyoto
Division of Internal Medicine, Kansai Denryoku Hospital (IN.) Osaka, Japan

Address reprint requests to: Toshihiro Yagura, M.D., The First Division, Department of Internal Medicine, Kyoto University School of Medicine, 53, Shogoin-Kawaramachi, Sakyo-Ku, Kyoto, 606, Japan.

Abstract

Properties of cyclic 3',5'-nucleotide phosphodiesterase in the 100,500 x g supernatant of the bovine thyroid were investigated. The enzyme activity was measured by a radioisotopic method using an anionic- exchange resin, and it was found that the activity was stimulated by Mg2+. Sephadex G-200 gel filtration separated the supernatant into an activating factor, which required the presence of Ca2+, and an enzyme form dependent on the factor. The molecular weights were estimated to be 25,000 and 130,000, respectively. There appeared to be another enzyme form of cAMP phosphodiesterase with different dependence on the activating factor as suggested by gel filtration, but this enzyme form could not be clearly separated. cGMP phosphodiesterase purified by gel filtration showed biphasic kinetic behavior in the absence of Ca2+ and the activating factor, whereas, in their presence, the Lineweaver- Burk plot gave a single Km. The activating mechanism of phosphodiesterase may play a role in the control of concentrations of intracellular cyclic 3',5'- nucleotides in the bovine thyroid.

Footnotes

* This study was supported by a research grant from the Intractable Diseases Division, Public Health Bureau, Ministry of Health and Welfare, Japan.

Received May 11, 1977.






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Copyright © 1978 by The Endocrine Society