based on the consideration that normal metabolic processes depend upon the activity of key enzymes ( and membrane carriers ) as modulated by regulatory factors ( hormones , diet , endogenous compounds , age , physical activity , environmental agents ) , metabolic disorders might be classified into two groups : ( i ) defects in enzyme synthesis , leading to enzyme deficiency ( classical inborn errors of metabolism ) or to qualitative ( structural ) enzyme alterations ( entailing unresponsiveness to regulation ) , in the presence of normal regulatory factors ;
C0025517
metabolic disorders
C0149676
enzyme deficiency