Assignment of the gene of mitochondrial branched chain aminotransferase (BCAT2) to sheep chromosome band 14q24 and to cattle and goat chromosome bands 18q24 by in situ hybridization

Branched chain aminotransferase (EC 2.6.1.42) is the first enzyme involved in the catabolic pathway of branched chain amino acids. Its activity is much lower in sheep than in rats (Papet et al., 1988). In order to investigate the biochemical basis of such a difference, we recently cloned the cDNA corresponding to the sheep mitochondrial branched chain aminotransferase gene BCAT2 (Faure et al., 1998). Human BCAT2 has previously been mapped to chromosome 19 using somatic cell hybrids (Bledsoe et al., 1997). The 929-bp cDNA fragment of sheep BCAT2 reveals 85, 81 and 80% identity with human, rat and mouse sequences, respectively. The BCAT2 sequence homology among sheep, cattle and goat, which are evolutionarily closer species, is likely higher than 95% as reported for milk proteins (Vilotte et al., 1992; Provot et al., 1989). The sheep probe has been used to assign BCAT2 to sheep chromosome band 14q24 and to cattle and goat chromosome bands 18q24 by in situ hybridization.