The enzymic formation of acetylglutamate has been studied in Chlorella vulgaris extracts. Acetyl CoA and N2-acetyl-l-ornithine served as substrates for glutamate acetylation whereas acetylphosphate, N5-acetyl-l-ornithine, and N2-acetyl-2,4-diamino butyrate were ineffective. Acetyl CoA-glutamate transacetylase and acetylornithine-glutamate transacetylase activities have been purified over 180-fold with no indication of any separation of activities. The acetyl CoA activity was more labile than acetylornithine activity so that preparations having acetylornithine-glutamate transacetylase activity but no acetyl CoA-glutamate transacetylase activity were obtained. The two acetylating activities appear to be properties of one enzyme with one portion more easily denatured.