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Comment

The major solutes in bile are N-acyl conjugates of cholanoates (C24 bile acids) with glycine or taurine. These bile acid-amino acid conjugates serve as detergents in the gastrointestinal tract. Bile acid-amino acid conjugates are formed in the liver via a 2-step pathway. The first reaction converts a bile acid to an acyl-CoA thioester and is catalyzed by the microsomal enzyme, cholyl-CoA synthetase (EC 6.2.1.7). The second reaction transfers the bile acid moiety from the acyl-CoA thioester to either glycine or taurine, and is catalyzed by bile acid-CoA:amino acid N-acyltransferase (BAAT\; EC 2.3.1.65).(from OMIM) Familial hypercholanemia is characterized by elevated serum bile acid concentrations, itching, and fat malabsorption. Carlton et al. (2003) studied this disorder in 17 individuals in 12 families of Lancaster County Old Order Amish descent. In 6 families, affected individuals were homozygous for a missense mutation in the gene encoding tight junction protein-2 (TJP2). In 2 families, affected individuals were homozygous for an M76V mutation in BAAT. In 2 families, the affected individuals were homozygous for the TJP2 missense mutation and heterozygous for the BAAT mutation, and in 1 family affected individuals were homozygous for the BAAT mutation and heterozygous for the TJP2 mutation