The sam gene encodes the enzyme, S-adenosylmethionine hydrolase,
and causes delayed ripening. S-adenosylmethionine hydrolase
is capable of degrading and thus reducing S-adenosylmethionine
(SAM). The conversion of SAM to 1-aminocyclopropane-1-carboxylic
acid (ACC) is the first step in ethylene biosynthesis and the lack
of sufficient pools of SAM results in significantly reduced
synthesis of this phytohormone, which is known to play a key role
in fruit ripening.