Biomedical subjects
Publications and source records attributed to R E Torregrossa.
A minor phospholipid from Acinetobacter sp. HO1-N was identified as acyl-phosphatidylglycerol. Acyl-phosphatidylglycerol synthesis by outer-membrane preparations appeared to be a result of phospholipase A activity.
An outer membrane phospholipase A active against phosphatidylglycerol and phosphatidylethanolamine was characterized from Acinetobacter sp. HO1-N.
Triacyl-lysocardiolipin (triacyl-LCL) and diacyl-LCL were isolated from Acinetobacter sp. HO1-N, and their structures were determined by chemical, physical, and enzymatic procedures. Deacylation of triacyl-LCL and diacyl-LCL yielded bis-glycerylphosphorylglycerol. Periodate oxidation of both lysolipids was negative. Diglyceride and 2-monoglyceride resulted from the acetic acid hydrolysis of triacyl-LCL, whereas 2-monoglyceride was the sole product obtained from diacyl-LCL. Cardiolipin (CL)-specific phospholipase D treatment of triacyl-LCL yielded lysophosphatidylglycerol and phosphatidic acid. Pancreatic lipase treatment of CL yielded triacyl-LCL and diacyl-LCL. 31P nuclear magnetic resonance spectrometry showed two resonance peaks separated by 40 HZ for CL, two overlapping peaks separated by 14 HZ for triacyl-LCL, and one peak for diacyl-LCL. The proportion of lysocardiolipin increased as a function of cell age, representing 2 to 3% of the total phospholipids in early- and mid-exponential growth, 5 to 7% in late-exponential growth, and 12% in the stationary growth phase.
A phospholipase A1 activity that hydrolyzed cardiolipin to triacyl- and diacyl-lysocardiolipin was localized in outer membrane preparations derived from Acinetobacter sp. HO1-N. The specific activity of the enzyme derived from hexadecane-grown cells was 2.5 to 3 times higher than that derived from NBYE-grown cells. An apparent Km of 2.22 mM was determined, although inhibition kinetics resulted at the higher cardiolipin substrate concentrations. Optimal reaction conditions established on metal requirements. Enzyme activity was obligately dependent on Triton X-100 (0.5%) and was inhibited by cationic and anionic detergents. Cardiolipin-specific phospholipase D converted triacyl-lysocardiolipin to lysophosphatidylglycerol and phosphatidic acid. The specific activity of this enzyme was approximately 100 times greater than that reported for other membrane preparations derived from microorganisms.