Guanine Nucleotide‐Binding Protein Regulation of Microsomal Phospholipase D Activity of Canine Cerebral Cortex

Zhuo Qian, Padala V. Reddy, Lester R Drewes

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Abstract: The hydrolytic activity of microsomal phospholipase D from canine cerebral cortex was measured by a radiochemical assay using 1,2‐dipalmitoyl‐sn‐glycerol‐3‐phosphoryl[3H]choline and 1‐palmitoyl‐2‐[9, 10(n)‐3H]palmitoyl‐sn‐glycerol‐3‐phosphorylcholine as the exogenous substrates. Of several detergents tested, Triton X‐100 was found to be the most effective in allowing expression of phospholipase D hydrolytic activity. The microsomal phospholipase D does not require any metal ion for its hydrolytic activity. Calcium and magnesium were slightly inhibitory between concentrations of 1 and 4 mM, but zinc was greatly inhibitory, causing a loss of >90% activity at the 4 mM concentration. Nonhydrolyzable guanine nucleotide analogues such as guanosine 5′‐(3‐O‐thio)triphosphate and guanyl‐5′‐yl‐(β,γ‐methylene)diphosphonate but not guanosine 5′‐(2‐thio)diphosphate were able persistently to stimulate phospholipase D hydrolytic activity at micromolar concentrations. Guanosine 5′‐(2‐thio)diphosphate was capable of partially blocking guanosine 5′‐(3‐O‐thio)triphosphate stimulation of phospholipase D. Aluminum fluoride was also able to cause a two‐ to threefold increase in hydrolytic activity of the phospholipase D. Cholera toxin had a stimulatory effect on the hydrolytic activity of phospholipase D, whereas islet‐activating protein pertussis toxin had no effect. These results indicate that regulation of microsomal phosphatidylcholine phospholipase D activity by the guanine nucleotide‐binding protein(s) in canine cerebral cortex may play an important role in signal transduction processes as well as in brain choline metabolism.

Original languageEnglish (US)
Pages (from-to)1632-1638
Number of pages7
JournalJournal of Neurochemistry
Volume54
Issue number5
DOIs
StatePublished - May 1990

Keywords

  • Choline
  • Guanine nucleotide
  • Guanine nucleotide‐binding protein
  • Microsomes
  • Phosphatidylcholine
  • Phospholipase D

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