Catalyzes the formation of S-adenosylmethionine from methionine and ATP. The reaction comprises two steps that are both catalyzed by the same enzyme: formation of S-adenosylmethionine (AdoMet) and triphosphate, and subsequent hydrolysis of the triphosphate.

(UniProt, P40320)

Body size and bristles reduced in heterozygotes; irregular facets in upper half of eye. Heterozygous females virtually sterile at temperatures above 18; surviving offspring frequently have missing legs or halteres, somewhat narrowed wings, and reduced bristles. Homozygotes lethal. Selected on the basis of a dominant suppressor of zeste phenotype. Characterized by relatively frequent reversions of all features of the phenotype save homozygous lethality. One such revertant found to be deficient for the tip of 2L, suggesting a gain of function rather than haplo insufficiency as the nature of the mutation (Kennison).