Catalyzes the formation of S-adenosylmethionine from methionine and ATP. The overall synthetic reaction is composed of two sequential steps, AdoMet formation and the subsequent tripolyphosphate hydrolysis which occurs prior to release of AdoMet from the enzyme (By similarity). Methionine adenosyltransferase 1 SAM1 394 MAAETFLFTSESVNEGHPDKLCDQVSDAVLDACLAQDPDSKVACETCTKTNMVMVFGEITTKATVDYEKIVRDTCRDIGFISDDVGLDADHCKVLVNIEQQSPDIAQGVHGHFTKRPEEVGAGDQGIMFGYATDETPELMPLTHMLATKLGARLTEVRKNGTCAWLRPDGKTQVTIEYLNEGGAMVPVRVHTVLISTQHDETVTNDEIAADLKEHVIKPVIPGKYLDENTIFHLNPSGRFVIGGPHGDAGLTARKIIIDTYGGWGAHGGGAFSGKDPTKVDRSGAYIARQAAKSIIASGLARRCIVQISYAIGVPEPLSVFVDSYGTGKIPDREILKLVKENFDFRPGMITINLDLKKGGNRFIKTAAYGHFGRDDADFTWEVVKPLKFDKASA S-adenosylmethionine synthase 1 METK1_HORVU