The size of enzymes acetylating alpha-melanocyte-stimulating hormone and beta-endorphin

Acetylation of alpha-melanocyte-stimulating hormone and beta-endorphin in a granule fraction from the rat pituitary neurointermediate lobe was examined by radiation inactivation. Target sizes obtained were 71 +/- 12 and 76 +/- 9 kDa, respectively. These data suggest that a single enzyme species may be responsible for acetylation of the two substrates. A similar analysis of alpha-melanocyte-stimulating hormone acetylation in the rat lens revealed a complex inactivation curve which could be explained by the presence of at least two different enzyme molecules, one of 86 and the other greater than 200 kDa.