The role of G protein in the activation of phospholipase C from bovine brain / 영남의대학술지

ABSTRACT

The objective of the present study was to identify the characteristics of phospholipase C (PLC) isozymes purified from bovine brain and to investigate their interrelationship with G protein. The purified PLC isozymes β, γ and δ were obtained and the characteristics of PLC activity on various concentrations of free Ca²⁺ were observed. The activity of PLC was increased with increasing Ca²⁺ concentration and the activity PLC δ was increased higher in the presence of phosphatidyl choline (PC) than in the absence of PC. For vesicle formation as the structure of cell membrane, cholic acid and deoxycholic acid as detergent on phosphatidylinositol bisphosphate (PIP₂) substrate containing PC were used, and then the activity of PLC isozymes were increased with increasing concentration of cholate, from 0.2% to 1% and were increased slightly in deoxycholate. In the PIP₂ containing phospholipid and glycolipid as brain extract, the activity of PLC isozymes were checked in 0.2-1% cholic acid. The activities of PLC isozymes were continuously increased up to 1% cholic acid. The quantitation of PLC isozymes from several bovine organs by radioimmunoassay was made. Brain was the most sufficient organ in terms of amount of PLC β and δ. A large amount of PLC δ was existed in adrenal gland. The binding capacity of GTPrS and G protein was observed and other observations of the binding effect of GTPrS-G protein and PLC monoclonal Ab-Protein A from tissue homogenate with PLC were made. From the observation the binding capacity was revealed the range of 0.11-1.49%. The effects of each type of G protein on the percent activity of purified PLC isozymes were observed. From the observation, activities of isozymes were increased in Goa & Gmix, and the activities of PLC β and δ were increased in Gβγ and Gia. Activities of PLC β and γ were decreased in Gta but PLC δ increased.