4alpha-methyl-5alpha-cholest-8-en-3-one + CO2 + NADH => 4alpha-carboxy-4beta-methyl-5alpha-cholest-8-en-3beta-ol + NAD(+)
4alpha-methyl-5alpha-cholest-8-en-3-one + co2 + nadh => 4alpha-carboxy-4beta-methyl-5alpha-cholest-8-en-3beta-ol + nad(+)