The conversion of exogenous retinol and related compounds into retinyl phosphate mannose by adult Brugia pahangi in vitro

Abstract

Adult B. pahangi took up and incorporated .beta.-carotene and free retinol in vitro. The uptake of retinol was 50 times greater than that of .beta.-carotene under similar incubation conditions. .beta.-Carotene was almost entirely metabolized, primarily to retinol. The metabolism of retinol by B. pahangi in vitro was less extensive, with a variety of retinoids tentatively identified, including retinyl phosphate (Ret-P), retinyl phosphate mannose (Ret-P-Man) and anhydroretinol as minor metabolites. B. pahangi microsomes also biosynthesized Ret-P-Man from exogenous Ret-P and GDP-mannose, but not from endogenous lipid acceptors alone. In this circumstance an unidentified lipid appeared to be mannosylated by B. pahangi. The rate of mannose transfer to exogenous Ret-P by B. pahangi microsomes was 150 pmol .cntdot. min-1 .cntdot. (mg of protein)-1. Ret-P-Man synthetase activity from B. pahangi and rat liver microsomes had an absolute requirement for bovine serum albumin and MnCl2, and occurred in the absence of detergent. The results suggest a biochemical role for vitamin A in B. pahangi, possibly in filarial glycoprotein synthesis.