Medical and Veterinary Importance of the Moonlighting Functions of Triosephosphate Isomerase.

Triosephosphate isomerase is the fifth enzyme in glycolysis and its canonical function is the reversible isomerization of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Within the last decade multiple other functions, that may not necessarily always involve catalysis, have been described. These include variations in the degree of its expression in many types of cancer and participation in the regulation of the cell cycle. Triosephosphate isomerase may function as an auto-antigen and in the evasion of the immune response, as a factor of virulence of some organisms, and also as an important allergen, mainly in a variety of seafoods. It is an important factor to consider in the cryopreservation of semen and seems to play a major role in some aspects of the development of Alzheimer's disease. It also seems to be responsible for neurodegenerative alterations in a few cases of human triosephosphate isomerase deficiency. Thus, triosephosphate isomerase is an excellent example of a moonlighting protein.

Identification and analysis of a Cu/Zn superoxide dismutase from Haliotis diversicolor supertexta with abalone juvenile detached syndrome.

A partial cDNA sequence of a putative Cu/Zn superoxide dismutase (SOD) from Haliotis diversicolor supertexta with abalone juvenile detached syndrome (AJDS) was isolated by suppression subtractive hybridization library screening. The full 988 base pair (bp) abalone Cu/Zn SOD cDNA representing full cDNA coding sequence was obtained by rapid amplification of cDNA ends (RACE), and included a 462-bp open reading frame encoding 154 amino acids, plus 49 bp of 5'-, and 477 bp of 3'-untranslated region. The coding sequence shared high similarity and identity with known Cu/Zn SODs. The deduced amino acids contained two typical Cu/Zn SOD motifs and the conserved geometry active sites. Moreover, the cysteines involved in dimer formation, and the copper- and zinc-binding sites were conserved. Recombinant abalone Cu/Zn SOD (abSOD) was expressed in Escherichia coli, purified under denaturing conditions, and refolded by direct buffer exchange or gel gradient recovery. The activity of the purified protein was enhanced by 1 microM Cu(2+) or 1 microM Cu(2+) plus 1 microM Zn(2+). The transcription of abSOD was significantly increased in AJDS abalones compared to controls, while protein expression and SOD enzyme activity both decreased significantly, suggesting that SOD may play an important role in AJDS, and that the disease etiology may be related to environmental stress.

Comparison of the tyrosine aminotransferase cDNA and genomic DNA sequences of normal mink and mink affected with tyrosinemia type II.

Type II tyrosinemia, designated Richner-Hanhart syndrome in humans, is a hereditary metabolic disorder with autosomal recessive inheritance characterized by a deficiency of tyrosine aminotransferase activity. Mutations occur in the human tyrosine aminotransferase gene, resulting in high levels of tyrosine and disease. Type II tyrosinemia occurs in mink, and our hypothesis was that it would also be associated with mutation(s) in the tyrosine aminotransferase gene. Therefore, the transcribed cDNA and the genomic tyrosine aminotransferase gene were sequenced from normal and affected mink. The gene extended over 11.9 kb and had 12 exons coding for a predicted 454-amino-acid protein with 93% homology with human tyrosine aminotransferase. FISH analysis mapped the gene to chromosome 8 using the Mandahl and Fredga (1975) nomenclature and chromosome 5 using the Christensen et al. (1996) nomenclature. The hypothesis was rejected because sequence analysis disclosed no mutations in either cDNA or introns that were associated with affected mink. This suggests that an unlinked gene regulatory mutation may be the cause of tyrosinemia in mink.