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At least 433 records · Page 24Linked to original sources
PubMed1989

Mutation of Bacillus firmus OF4 to duramycin resistance results in substantial replacement of membrane lipid phosphatidylethanolamine by its plasmalogen form.

Mutant strains of alkalophilic Bacillus firmus OF4 that were selected for resistance to duramycin had greatly reduced levels of membrane diacylphosphatidylethanolamine, as had been found in studies of such mutants of Bacillus subtilis. In the B. firmus strains, however, substantial levels of plasmenylethanolamine were found. This is an unusual membrane component for an aerobic eubacterium, but the presence of trace amounts even in the wild type was confirmed in experiments with 32Pi-labeled growth medium. The membrane lipid composition of the duramycin-resistant strains had several other changes that also left alkalophilic growth unimpaired.

Anti-Bacterial Agents↗
PubMed1998

Selective hydrolysis of plasmalogens in endothelial cells following thrombin stimulation.

The present study was performed to characterize thrombin-stimulated phospholipase A2 (PLA2) activity and the resultant release of lysophospholipids from endothelial cells. The majority of PLA2 activity in endothelial cells was membrane associated, Ca2+ independent, and arachidonate selective. Incubation with thrombin increased membrane-associated PLA2 activity using both plasmenylcholine and alkylacyl glycerophosphocholine substrates in the absence of Ca2+, with no increase in activity observed with phosphatidylcholine substrate. The increased PLA2 activity was accompanied by arachidonic acid and lysoplasmenylcholine (LPlasC) release from endothelial cells into the surrounding medium. Thrombin-induced changes were duplicated by stimulation with the thrombin-receptor-directed peptide SFLLRNPNDKYEPF. Pretreatment with the Ca2+-independent PLA2 inhibitor bromoenol lactone blocked thrombin-stimulated increases in PLA2 activity, arachidonic acid, and LPlasC release. Stimulation of protein kinase C (PKC) increased basal PLA2 activity and LPlasC production. Thrombin-stimulated PLA2 activity and LPlasC production were enhanced with PKC activation and completely prevented with PKC downregulation. Thus thrombin treatment of endothelial cells activates a PKC-activated, membrane-associated, Ca2+-independent PLA2 that selectively hydrolyzes arachidonylated, ether-linked phospholipid substrates, resulting in LPlasC and arachidonic acid release.

Animals↗
PubMed1993

Pseudo infantile Refsum's disease: catalase-deficient peroxisomal particles with partial deficiency of plasmalogen synthesis and oxidation of fatty acids.

Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum's disease are genetic disorders characterized by the virtual absence of catalase-positive peroxisomes and a general impairment of peroxisomal functions. Recent studies in these three disorders have provided morphologic evidence of peroxisomal "ghosts" of density 1.10 g/cm3 that contain membrane proteins but lack a majority of the matrix enzyme activities. We report here the biochemical studies in a female infant with clinical features of infantile Refsum's disease whose liver and fibroblasts contained cytosolic catalase but no catalase-positive peroxisomes. Oxidation of phytanic and pipecolic acids was severely impaired, whereas oxidation of very-long-chain fatty acids and dihydroxyacetone phosphate acyltransferase activity were only partially decreased. Immunoblot analysis showed that the three peroxisomal beta-oxidation enzymes (acyl-CoA oxidase, enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase) were detectable in liver tissues. The 3-ketoacyl-CoA thiolase was of the mature form (41 kD), in contrast with other peroxisomal disorders with multiple enzyme deficiencies. The majority of these peroxisomal enzyme activities were associated with two subcellular membrane vesicle fractions lacking catalase: one had the density of normal peroxisomes (1.17 g/cm3), the other, yet undescribed, a lower density (1.137 g/cm3). This suggests that peroxisomes (density = 1.17 g/cm3) and structures with lower density (density = 1.137 g/cm3) found in this patient's cultured skin fibroblasts, although lacking catalase, contained functional peroxisomal enzymes. This distinguishes this disorder from other disorders of peroxisome biogenesis.

Acatalasia↗