title: Equal inhibition of HIV replication by stereoisomers of phosphatidyl-azidothymidine. Lack of stereospecificity of lysosomal phospholipase A1.
abstract: Glycerol-1-P and glycerol-3-P stereoisomers of dipalmitoylphosphatidylazidothymidine were synthesized and found to have equal antiretroviral activity in HIV-infected HT4-6C cells. It was anticipated that the glycerol-1-P isomer would be less active because of slow metabolic conversion by cellular phospholipases A and C, but the antiretroviral results suggested that the human cell line (HT4-6C) may have phospholipases capable of hydrolyzing 2,3-dipalmitoyl-sn-glycerol-1-phospho-5'-azidothymidine (AZT). To evaluate this possibility, we purified lysosomal phospholipase A1, an enzyme known to play a major role in cellular phospholipid catabolism. This enzyme rapidly hydrolyzed both the sn-1 and sn-3 isomers of dipalmitoylphosphatidyl-AZT. We synthesized sn-2,3-dipalmitoyl-glycero-1-phosphocholine and found that it is also hydrolyzed readily by lysosomal phospholipase A1 although the Vmax, 59 mumol mg-1 h-1, is slightly lower than that of the sn-1,2-dipalmitoyl-glycero-3-phosphocholine, 89 mumol mg-1 h-1. In conclusion, our studies show that sn-2,3-dipalmitoyl-glycerol-1-phospho-AZT is equal in antiviral activity to sn-1,2-dipalmitoyl-glycero-3-phospho-AZT in HIV-infected HT4-6C cells. This surprising result is due in part to the lack of stereospecificity of lysosomal phospholipase A1.
authors.affiliation: Vical Incorporated, San Diego, California 92121.
authors.forename: R
authors.initials: R
authors.lastname: Kumar
authors.forename: M F
authors.initials: MF
authors.lastname: Gardner
authors.forename: D D
authors.initials: DD
authors.lastname: Richman
authors.forename: K Y
authors.initials: KY
authors.lastname: Hostetler
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D002460:Cell Line; D002855:Chromatography, Thin Layer; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008099:Liver / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology*; D010741:Phospholipases A / Q000302:isolation & purification / Q000378:metabolism*; D054466:Phospholipases A1; D051381:Rats; D013237:Stereoisomerism; D014779:Virus Replication / Q000187:drug effects; D015215:Zidovudine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000998:Antiviral Agents; D015215:Zidovudine; D010741:Phospholipases A; D054466:Phospholipases A1