sterol 24-C-methyltransferase activity delta24-methyltransferase activity delta(24)-methyltransferase activity MetaCyc:RXN3O-178 S-adenosyl-L-methionine:Delta24(23)-sterol methyltransferase activity EC:2.1.1.41 24-sterol C-methyltransferase activity delta(24)-sterol methyltransferase activity S-adenosyl-4-methionine:sterol delta24-methyltransferase activity zymosterol-24-methyltransferase activity phytosterol methyltransferase activity S-adenosyl-L-methionine:Delta(24(23))-sterol methyltransferase activity Catalysis of the reaction: S-adenosyl-L-methionine + 5-alpha-cholest-8,24-dien-3-beta-ol = S-adenosyl-L-homocysteine + 24-methylene-5-alpha-cholest-8-en-3-beta-ol. delta(24)-sterol C-methyltransferase activity SMT1 activity S-adenosyl-L-methionine:zymosterol 24-C-methyltransferase activity S-adenosyl-4-methionine:sterol Delta(24)-methyltransferase activity GO:0003838 delta24-sterol methyltransferase activity molecular_function RHEA:21131 C-methyltransferase activity S-adenosylmethionine-dependent methyltransferase activity