牛垂体前叶亚细胞组分中的生长激素激酶活性。

GH kinase activity in bovine anterior pituitary subcellular fractions.

作者信息

Wicks J R, Brooks C L

机构信息

Department of Veterinary Biosciences, The Ohio State University, Columbus 43210, USA.

出版信息

Endocrine. 1999 Feb;10(1):77-82. doi: 10.1385/ENDO:10:1:77.

DOI:10.1385/ENDO:10:1:77

PMID:10403574

Abstract

Growth hormone (GH) and prolactin (PRL) share significant structural homology. We have previously characterized the phosphorylation of bovine PRL and wish to determine whether a similar kinase activity phosphorylates bovine GH. Phosphorylation of bovine GH was performed using [alpha-32P]ATP labeling of subcellular fractions. Bovine GH phosphorylation was dependent on Zn2+ or Cu2+ with apparent Km's of 0.9 and 1.0 mM, respectively, and a pH maxima of 7.0. The apparent Km's of bovine GH kinase activity for exogenous bovine GH and ATP were 30 microM and 376 microM, respectively. Exogenous bovine PRL served as a competitive substrate, increasing the apparent Km for bovine GH by threefold compared to the Km determined without exogenous bovine PRL. We conclude: 1) in vitro phosphorylation of bovine GH occurs under conditions that are consistent with those found in anterior pituitary cells, and 2) a similar kinase activity phosphorylates both bovine PRL and GH.

摘要

生长激素（GH）和催乳素（PRL）具有显著的结构同源性。我们之前已对牛催乳素的磷酸化进行了表征，并且希望确定是否有类似的激酶活性使牛生长激素发生磷酸化。使用[α-32P]ATP对亚细胞组分进行标记来实现牛生长激素的磷酸化。牛生长激素的磷酸化依赖于锌离子（Zn2+）或铜离子（Cu2+），其表观米氏常数（Km）分别为0.9 mM和1.0 mM，最适pH为7.0。牛生长激素激酶活性对外源牛生长激素和ATP的表观米氏常数分别为30 μM和376 μM。外源性牛催乳素作为竞争性底物，与未添加外源性牛催乳素时测定的Km相比，使牛生长激素的表观Km增加了三倍。我们得出以下结论：1）牛生长激素的体外磷酸化发生在与垂体前叶细胞中发现的条件一致的情况下；2）类似的激酶活性使牛催乳素和牛生长激素都发生磷酸化。