obsolete 4alpha-carboxy-stigmasta-7,24(241)-dien-3beta-ol dehydrogenase/C4-decarboxylase activity (obsolete GO:0102182)
OBSOLETE. Catalysis of the reaction: 4alpha-carboxy-stigmasta-7,24(241)-dien-3beta-ol + NAD = avenastenone + NADH + carbon dioxide.