Galactose-1-phosphate uridyl transferase in density-fractionated erythrocytes

Summary Galactose-1-phosphate uridyl transferase (GALT), the deficient enzyme in classical galactosemia, was studied by Percoll-gradient age-fractionation of erythrocytes. For normal GALT, a rapid and substantial decrease in GALT activity and loss of most of two isozymes was found to occur in the reticulocyte fractions. The loss of activity was then followed by relative stabilization of both GALT-specific activity and microheterogeneity in mature and aging erythrocytes. When applied to the study of mutant GALT from galactosemic patients, the Percoll-gradient fractionation method permitted detection in the reticulocyte-enriched fractions of up to 5% of normal GALT-specific activity and an isoelectric focusing pattern essentially the same as that of normal GALT. Percoll-gradient fractionation of erythrocytes offers a simple and direct method to study characteristics of GALT activity and microheterogeneity in normal and galactosemic human erythrocytes.     

A new genetic variant of galactose-1-phosphate uridyl transferase

Summary The enzyme galactose-1-phosphate uridyl transferase (E.C. 2.7.7.12), which has an important function in the metabolism of galactose, exists in multiple molecular forms. The different phenotypes are genetically determined. They can be distinguished according to their electrophoretic mobility. The enzymatic activity of the different gene products varies within certain limits. A new phenotype of the enzyme has been detected in the red cells of a healthy individual. The electrophoretic migration of this phenotype is slower compared to the wild type and its enzymatic activity is lower, but still sufficient as not to cause galactosemia. An extensive family study revealed that the rare gene is inherited according to mendelian law. Independently the same gene product has been detected in two other, nonrelated individuals out of a total of 1668 samples tested. The gene frequency can therefore be estimated to 0.0009 in the Swiss population. We suggest that the new type be called Berne variant of galactose-1-phosphate uridyl transferase.     

Purification, properties, and isozyme pattern of galactose-1-phosphate uridyl transferase from calf liver.

Galactose-1-phosphate uridyl transferase was purified approximately 2000-fold from calf liver with a yield of 15%. The purification procedure involved ammonium sulfate fractionation, calcium phosphate-gel adsorption, and chromatography on DEAE-cellulose, hydroxylapatite, and Sephadex columns. The purified product demonstrated five protein bands on polyacrylamide-gel electrophoresis. Each band had transferase activity as five peaks of activity were observed on preparative polyacrylamide-gel electrophoresis. Galactose-1-phosphate uridyl transferase showed no requirement for divalent metals for activity. In contrast, it was inhibited by Mg²⁺ and other divalent metals. The purified enzyme but not the crude preparation was stimulated by sulfhydryl compounds. The enzyme was completely inhibited by low concentrations of p-hydroxymercuribenzoate.     

Variants of galactose-1-phosphate uridyl transferase in the Greek populations

Summary The frequency of variants of galactose-1-phosphate uridyl transferase was determined among the nine Greek populations by studying a sample of 1570 unselected individuals. Average frequency of normal allele GALT=0.942, galactosemia gene GALT ^G=0.0021 and the Duarte variant gene GALT ^D=0.0548 were observed. Frequency of galactosemia heterozygotes among Greeks was similar to that in other Caucasian populations, but the frequency of the Duarte variant was considerably higher. With the exception of two populations, one with low (Epirus) and one with high (Thrace) frequencies, the polymorphism of the Duarte variant displays very similar frequencies in the various Greek population groups.Supported by Grants HD 01 974 and GM 15 253 from the U.S. Public Health Service     

E. coli galactose-1-phosphate uridyl transferase: N-terminal and C-terminal sequences

Summary A modified procedure for the purification of E. coli galactose-1-phosphate uridyl transferase (E.C. 2.7.6.12) was developed which reproducibly gives pure enzyme. The purified enzyme was shown to be a dimeric protein with a subunit molecular weight of 41,000 and its amino acid composition and content of free sulfhydryl groups were determined. The N-terminal and C-terminal amino acid sequences were found to be NH₂-thr-gln-phe-asn-pro-val-asp and -ser(val leu)-ala-COOH respectively. This N-terminal sequence allowed the identification of the start of the transferase gene in the DNA sequence determined by GRINDLEY. Furthermore it appears to define a nine base intercistronic region between the epimerase and transferase genes.Abbreviations Cyclic AMP Cyclic adenosine 2¹5¹ monophosphate - DPN Diphosphopyridine nucleotide - UDP Uridine diphosphate - EDTA Ethylene diamine tetra acetic acid - SDS sodium dodecyl sulfate - NEM N-ethylmaleimide     

Polymorphism of human red cell galactose-1-phosphate uridyl transferase in Serbia, Yugoslavia

Phenotypes of human red cell galactose-1-phosphate uridyl transferase (GALT) were determined in 283 unrelated adults from Serbia (Yugoslavia). The gene frequencies were 0.959 for GALT N, 0.018 for GALT D and 0.023 for GALT N.     

Improved technique for electrophoresis of human galactose-1-P uridyl transferase (EC 2.7.7.12)

Summary A newly developed electrophoretic technique for human galactose-1-phosphate uridyl transferase confirms the multiple band patterns for the Duarte and Los Angeles variants. This represents the first confirmation for the Los Angeles variant. The observed frequencies of N, D, and LA types are similar to earlier reports for these variants.     

Probable linkage between the human galactose-1-P uridyl transferase locus and 9qh.

Evaluation of a family in which electrophoretic variants of the eznyme galactose-1-phosphate uridyl transferase (GALT) and 9qh variants occur demonstrates close linkage between these two traits: lod score of 3.67 at theta = 0. Taken with information indicating GALT is on the short arm of chromosome 9, these linkage data suggest that this locus is close to the centromere on the short arm of chromosome 9.     

On the molecular nature of the Duarte variant of galactose-1-phosphate uridyl transferase (GALT)

Galactosemia is an inborn error of galactose metabolism secondary to deficiency of galactose-1-phosphate uridyl transferase (GALT). GALT is a polymorphic enzyme and Duarte (D) is the most common enzyme variant. This variant is characterized by faster electrophoretic mobility and reduced activity. Duarte/galactosemia compound heterozygotes (D/G) are commonly identified in galactosemia newborn screening programs. However, these patients do not generally require treatment. By using a candidate mutation approach to define the molecular basis of the Duarte variant of GALT, a close association between the previously reported N314D polymorphism and the Duarte variant of GALT was found. We suggest that N314D encodes the D variant of GALT and that molecular testing for N314D might be useful to confirm a biochemical diagnosis of Duarte variant of GALT.     

Isoelectrofocusing of erythrocyte galactose 1 phospho uridyl transferase in a family with both galactosemia and duarte variants

Summary A family with the presence of the genes for both galactosemia and the Duarte variant is described. Galactose 1 phospho uridyl transferase has been studied not only by electrophoresis on starch gel, but also by isoelectrofocusing on thin-layer acrylamide.Normal and variant transferases were resolved into three bands, the isoelectric point of which was between 5.40 and 5.10 for the normal subjects, and between 5.25 and 4.95 for subjects with the Duarte variant.     

Pseudo-isoenzyme forms of liver prenyl transferase

Prenyl transferase of pig liver exists in two forms, A and B, the latter being more acidic than form A. The ratio of these two forms in initial extracts of the organ varies according to the presence or absence of a thiol reducing agent in the extraction medium. In the presence of 10 mM β-mercaptoethanol the two forms exist as an equilibrium mixture of ca. 70% form A and 30% form B. The latter, when separated and rechromatographed with β-mercaptoethanol reverts to approximate the same 7:3 ratio of forms A and B. In the absence of a thiol reducing agent form B does not change, but form A may be converted almost completely to form B after treatment with oxidized glutathione.     

Characterization of toad liver glutathione transferase

The major form of glutathione transferase from the toad liver previously designed as Bufo bufo liver GST-7.6 (A. Aceto, B. Dragani, T. Bucciarelli, P. Sacchetta, F. Martini, S. Angelucci, F. Amicarelli, M. Miranda and C. Di Ilio, Biochem. J. 289 (1993) 417-422) has been characterized. According to its partial amino acid sequence, the toad enzyme may be included in the pi class GST and named bbGST P2-2. However, bbGST P2-2 appears to be immunologically, structurally and kinetically distinct from any other members of pi family, including bbGST P1-1, suggesting that it may constitute a subset of pi class GST. The data support the hypothesis that the transition from aquatic to terrestrial life causes a switch of the GST amphibian pattern promoting the expression of a GST form (bbGST P2-2) able to counteract, with higher efficiency, the toxic effects of reactive metabolites of oxidative metabolism and those of hydrophobic xenobiotics.     

Study of a family with Los Angeles,Duarte, and classical galactosemia variants of galactose-1-phosphate uridyl transferase

We have described a family which has a combination of rare genetic alleles for the enzyme erythrocyte galactose-1-phosphate-uridyl transferase. The father has a combination of the Los Angeles and classical galactosemic alleles. The mother has a combination of the Duarte and classical galactosemic alleles. Their five children present various conbinations of these three alleles. One has classical galactosemia but she had, however, an atypical clinical presentation in that she survived for 8 months while being fed a normal diet. Despite this period of galactose ingestion she is of normal intelligence.