isorhapontigenin + S-adenosyl-L-methionine => 4'-O-methylisorhapontigenin + S-adenosyl-L-homocysteine + H(+)
isorhapontigenin + s-adenosyl-l-methionine => 4'-o-methylisorhapontigenin + s-adenosyl-l-homocysteine + h(+)
isorhapontigenin + S-adenosyl-L-methionine => 4'-O-methylisorhapontigenin + S-adenosyl-L-homocysteine + H(+)
isorhapontigenin + s-adenosyl-l-methionine => 4'-o-methylisorhapontigenin + s-adenosyl-l-homocysteine + h(+)