Possible regulation of hypothalamus and lung histidine decarboxylase activity by cAMP-dependent protein kinase

Z. Huszti, K. Magyar, J. Keleti

Research output: Contribution to journalArticle

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Abstract

Activity of crude histidine decarboxylases (HisDC) from the hypothalamus and the lungs, was markedly reduced by incubating with ATP · Mg, cAMP and cAMP-dependent protein kinase A, whereas activity of the crude glandular stomach enzyme changed only slightly under equal condition. The omission of one of these components failed to reduce HisDC activity by as much as the complete system. Addition of bovine heart (type II) or rat cerebellum protein kinase A (types I and II) inhibitor to the assay prevented enzyme inactivation; moreover, protein kinase A inhibitors permitted moderate activation under phosphorylating and control conditions. Cytosolic hypothalamus HisDC activity was elevated 2-2.2-fold by incubating the cytosol for 15 min in the presence of MnCl2, a known stimulator of phosphoprotein phosphatase; this was prevented when 20 mM NaF, a common inhibitor of phosphoprotein phosphatase, was added to the cytosol. The apparent K(m) of ATP · Mg-treated hypothalamus HisDC for hisitidine was elevated 5-10-fold compared to controls, whereas the V(max) was approximately the same. Under this condition, the K(m) was calculated as high as 0.5-2.2 mM (depending on phosphorylating conditions), while controls had a K(m) of 0.1-0.3 mM (depending on the initial phosphorylating states). Addition of rabbit muscle (type I), bovine heart (type II) or rat cerebellum (types I and II) inhibitor of protein kinase A, to the phosphorylating mixture, abolished the difference in K(m) between control and ATP · Mg-treated HisDC. Moreover, rat cerebellum protein kinase A inhibitors increased V(max) to above the control level; while 20 mM NaF (inhibitor of phosphoprotein phosphatase) decreased V(max) to approximately one half of that of the controls. These data indicate that HisDC activity in the hypothalamus and the lungs, but not in the stomach, is affected in oppositely by protein kinase A and phosphoprotein phosphatases.

Original languageEnglish
Pages (from-to)191-196
Number of pages6
JournalEuropean Journal of Biochemistry
Volume197
Issue number1
Publication statusPublished - 1991

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Histidine Decarboxylase
Cyclic AMP-Dependent Protein Kinases
Hypothalamus
Phosphoprotein Phosphatases
Lung
Cerebellum
Rats
Adenosine Triphosphate
Protein Kinase Inhibitors
Cytosol
Stomach
Level control
Enzyme Assays
Enzymes
Muscle
Assays
Chemical activation
Rabbits
Muscles

ASJC Scopus subject areas

  • Biochemistry

Cite this

Possible regulation of hypothalamus and lung histidine decarboxylase activity by cAMP-dependent protein kinase. / Huszti, Z.; Magyar, K.; Keleti, J.

In: European Journal of Biochemistry, Vol. 197, No. 1, 1991, p. 191-196.

Research output: Contribution to journalArticle

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