The determination of plasmalogenase activity in isolated oligodendroglia from bovine brain white matter.

by the decrease in incorporation of labelled methyl groups from enzymically synthesized S-adenosylmethionine into basic protein by spinal-cord protein methylase activity (Table 1). Electrophoresis of the labelled protein precipitate on acetic acidhrea-polyacrylamide gels (Deibler et al., 1972), followed by autoradiography of the gels, indicated that only the myelin basic protein was detectably labelled. Autoradiography of peptide 'maps' of labelled peptides obtained by digestion with trypsin (Bates ef al., 1975) demonstrated that radiolabel was incorporated into the peptide containing arginine107 (Eylar et al., 1971). These results have demonstrated the activity of methionine adenosyltransferase and protein (arginine) methyltransferase activity in the cytoplasmic fraction of mouse spinal cord. The protein (arginine) methyltransferase appears to have a specificity for arginine-107 of myelin basic protein from bovine spinal cord. This observation is in accord with results obtained with guinea-pig enzyme and human myelin basic protein acceptor (Baldwin & Carnegie, 1971) and suggests that specific structural features of myelin basic protein in the region of arginine-107 are similar in a number of species. The inhibition of myelin basic protein arginine methylase by inhibiting the synthesis of S-adenosylmethionine with 1-aminocyclopentane-1-carboxylic acid indicates that the details of this particular post-translational modification may now be investigated both in virro and in vivo. We are grateful to the Medical Research Council and the Sir Halley Stewart Trust for financial support. W. J . is a Sir Halley Stewart Research Professor.