GLYCERYL-ETHER MONOOXYGENASE [EC-1.14.16.5] .9. STEREOSPECIFICITY OF THE OXYGENASE REACTION

(2RS,1'R)-[1'-H-3(1)]-and 2RS,1'S)-[1'-H-3(1)]-Hexadecyloxypropane-1,2 -diols (chimyl alcohols) have been prepared and their stereochemistry has been confirmed by synthesizing the [H-2(1)]-analogues using simila r procedures. When they were used as substrates for glyceryl-ether mon ooxygenase from rat liver in the presence of oxygen and (RS)-6-methyl- 5,6,7,8-tetrahydropterin as co-factor, the 1'S-isomer released 37% of its tritium into the aqueous buffer after 20 mins, whereas the 1'R-iso mer released only 6.5% showing that the reaction was stereospecific fo r the pro-H-S hydrogen atom of the glyceryl ether substrate. This was in agreement with the kinetic parameters of unlabelled -(2RS)-3-, (2RS ,1'R)-3-[1'-H-2(1)]-,(2RS,1'S)-3-[1'-H-2(1)]- and RS)-3-[1',1'-H-2(2)] -hexadecyloxypropane-1,2-diols where the apparent K-m values were abou t the same (49.4, 53.7, 49.3 and 54.0 mu M respectively) but the appar ent maximum velocities (V-max in nmol min(-1) mg(-1) protein) of the f irst two substrates (37.5 and 37.5) were faster than the latter two su bstrates (22.5 and 23.6), consistent with the pro-H-S hydrogen atom be ing replaced by the hydroxy group and a primary deuterium isotope effe ct of similar to 1.6.