| IDENTIFICATION OF SPECIES OF ORIGIN |
Species of Origin Confirmed by Nucleoside Phosphorylase Isoenzyme Electrophoresis |
| |
| UDP-glucose--hexose-1-phosphate uridylyltransferase |
According to the submitter, biochemical test results for this subject showed decreased enzyme activity. EC Number: 2.7.7.12; 0% activity. |
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| Gene |
GALT |
| Chromosomal Location |
9p13 |
| Allelic Variant 1 |
606999.0010; GALACTOSEMIA |
| Identified Mutation |
SER135LEU; Baker et al. (1966) described black patients with classic galactosemia who lacked GALT activity in their erythrocytes and yet were able to oxidize a substantial amount of labeled galactose to CO2 in vivo (Segal and Cuatrecasas, 1968). Liver and intestinal mucosa biopsy specimens from these patients expressed about 10% of normal GALT activity. This apparent tissue specificity of GALT enzyme expression was labeled the 'negro variant' of galactosemia. Lai et al. (1996) demonstrated that the underlying mutation is a C-to-T transition at bp1158 of the GALT gene that results in a serine-to-leucine substitution at codon 135 (S135L). Population screening was performed using a restriction enzyme assay; the mutation abolishes a TAQI recognition site. The S135L mutation was not found in 84 white patients with homozygous galactosemia or in 87 white control subjects without galactosemia. One S135L allele was found out of the 100 GALT alleles in 50 black subjects; 16 out of 32 alleles in 16 galactosemic patients were of the S135L type. (Also in 1 patient with galactosemia, the S135L mutation was maternal in origin; the patient had a black mother and a white father.)
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| Gene |
GALT |
| Chromosomal Location |
9p13 |
| Allelic Variant 1 |
T292T; GALACTOSEMIA (POLYMORPHISM) |
| Identified Mutation |
THR292THR |
| |
| Gene |
GALT |
| Chromosomal Location |
9p13 |
| Allelic Variant 1 |
H315H; GALACTOSEMIA (POLYMORPHISM) |
| Identified Mutation |
HIS315HIS |
| |
| Gene |
GALT |
| Chromosomal Location |
9p13 |
| Allelic Variant 2 |
606999.0008; GALACTOSEMIA |
| Identified Mutation |
PHE171SER; Reichardt et al. [Biochemistry 31: 5430-5433 (1992)] characterized two galactosemia (230400) mutations, L74P (606999.0007) and F171S, and one polymorphism, S135L, in the GALT gene. Both mutations resulted in reduced enzymatic activity on expression studies, whereas the polymorphism resulted in near normal activity. Both mutations involved evolutionarily conserved residues, while the polymorphism occurred in a nonconserved domain. |