3-MCC catalyzes the carboxylation of 3-methylcrotonyl-CoA to 3-methylglutaconyl-CoA within the leucine catabolic pathway (Fig.
Deficiency of 3-MCC causes accumulation of 3-methylcrotonyl-CoA, which undergoes hydration to form 3-hydroxyisovaleryl-CoA (Fig.
This enzyme catalyzes the conversion of isovalery-CoA to 3-methylcrotonyl-CoA
, and a deficiency of this enzyme results in toxic accumulation of isovaleric acid and derivative organic acids.
We received a phone call from our children's pediatrician telling us that Damian's newborn screening had come back abnormal for 3-methylcrotonyl-CoA
carboxylase deficiency, or 3MCC.
Elevations in C5-OH acylcarnitine are indicative of a variety of pathologies, including 3-methylcrotonyl-CoA carboxylase deficiency, and have frequently resulted in a diagnosis of this deficiency in the mother rather than in the newborn (5).
Newborn screen findings can reveal maternal defects in the case of several inborn errors of metabolism, including 3-methylcrotonyl-CoA carboxylase deficiency and carnitine transport defect, and also can reveal nutritional deficits in the mother.
The hydratase deficiency in these patients was identified by use of a radioactive enzyme assay measuring three consecutive steps of leucine degradation, from 3-methylcrotonyl-CoA to acetoacetic acid (12).
3-Methylglutaconyl-CoA hydratase, 3-methylcrotonyl-CoA carboxylase and 3-hydroxy-3-methylglutarylCoA lyase deficiencies: a coupled enzyme assay useful for their detection.
Carboxylase Deficiency--Symptoms may include hypotonia, muscle atrophy, seizures, and dermatological changes.
C50H is increased in 3-methylcrotonyl-CoA
carboxylase deficiency, 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, and 3-methylglutaconyl-CoA hydratase deficiency, whereas 2-methyl-3-hydroxybutyrylcarnitine is increased in [beta]-ketothiolase deficiency and 2-methyl-3-hydroxybutyrl-CoA dehydrogenase deficiency (118).
beta]-ketothiolase deficiency 3-Methylcrotonylglycine 3-Methylcrotonyl-CoA
carboxylase deficiency; multiple carboxylase deficiency; HMG-CoA lyase deficiency 3-Methylglutaconate (37-42) 3-Methylglutaconyl-CoA hydratase deficiency (methylglutaconic aciduria type I); HMG-CoA lyase deficiency; 3-methylglutaconic aciduria (other than type I); respiratory chain defects (e.
beta]-KETOTHIOLASE, 3-HYDROXY-3-METHYLGLUTARYL-COA LYASE (HMG), AND 3-METHYLCROTONYL-COA
CARBOXYLASE (MCC) DEFICIENCY AND MCD