GENE STRUCTURE AND MUTATIONS OF GLUTARYL-COENZYME A DEHYDROGENASE - IMPAIRED ASSOCIATION OF ENZYME SUBUNITS THAT IS DUE TO AN A421V SUBSTITUTION CAUSES GLUTARIC ACIDEMIA TYPE-I IN THE AMISH

The structure of the human glutaryl coenzyme A dehydrogenase (GCD) gen e was determined to contain 11 exons and to span similar to 7 kb. Fibr oblast DNA from 64 unrelated glutaric acidemia type I (GA1) patients w as screened for mutations by PCR amplification and analysis of SSCP. F ragments with altered electrophoretic mobility were subcloned and sequ enced to detect mutations that caused GA1. This report describes the s tructure of the GCD gene, as well as point mutations and polymorphisms found in 7 of its 11 exons. Several mutations were found in more than one patient, but no one prevalent mutation was detected in the genera l population. As expected from pedigree analysis, a single mutant alle le causes GA1 in the Old Order Amish of Lancaster County, Pennsylvania . Several mutations have been expressed in Escherichia coli, and all p roduce diminished enzyme activity. Reduced activity in GCD encoded by the A421V mutation in the Amish may be due to impaired association of enzyme subunits.