Resolution of myocardial phospholipase C into several forms with distinct properties.
Phospholipase C activity capable of hydrolysing phosphatidylinositol in bovine heart was resolved into four forms (I-IV) by ion-exchange chromatography. Some of these forms could only be detected if the assay was performed at acidic pH (I and IV) or in the presence of deoxycholate (II). Gel-filtration chromatography indicated that the four forms had different molecular weights in the range 40000-120000. I, II and III all had pH optima in the range 4.5-5.5. However, the major form (III) also had substantial activity at pH 7.0 and above. The activities of I, II and III at pH 7.0 were stimulated by deoxycholate; this effect was most marked with I and II, which had very low activity at this pH. All forms of the enzyme were inhibited by EGTA and required 2-5 mM-CaCl2 for maximal activity. When the fractions eluted from the ion-exchange and gel-filtration columns were assayed with polyphosphoinositides as substrates there was a close correspondence to the elution profile obtained with phosphatidylinositol as substrate; there was no evidence for the existence in heart of phospholipase C activities specific for individual phosphoinositides.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007527:Isoenzymes / Q000378:metabolism*; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D010716:Phosphatidylinositols / Q000378:metabolism; D010740:Phospholipases / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*
D007527:Isoenzymes; D010716:Phosphatidylinositols; D010740:Phospholipases; D010738:Type C Phospholipases; D002118:Calcium