[Inborn errors of metabolism due to mutations in isoenzyme genes]

Technical advances in molecular biology have permitted the detailed study of specific genes in the pathogenesis of inborn errors of metabolism. Analysis of inborn errors of metabolism due to mutations in isoenzyme genes are summarized in this paper. GM2-gangliosidosis results from a deficiency in the activity of beta-N-acetyl hexosaminidase (HEX), and produces two types of diseases: Tay-Sachs and Sandohoff disease, also known as HEX isoenzyme (HEXA and HEXB, respectively) deficiencies. Gene analysis revealed a 5'-defect and point mutation in patients with Tay-Sachs disease. Lactic dehydrogenase has two subunits and two types of deficiency of these two subunits (M and H). Gene analysis revealed a deletion consisting of 20 bp in exon 6 in patients with M subunit deficiency and one of 2 bases in exon 3 in those with H subunit deficiency.