Observations on the isoenzymes of aspartate aminotransferase in equine tissues and serum.

The research article focuses on the study of the distribution of aspartate aminotransferase (AST) isoenzymes in horse tissues to determine the possibility of identifying their organ of origin when the amount of AST in the serum is increased.

Study on Isoenzymes of Aspartate Aminotransferase

• The research looks into the distribution of aspartate aminotransferase (AST) isoenzymes in horse tissues, probing whether the source organ can be determined when the total AST serum activity is elevated.
• AST is an essential enzyme involved in amino acid metabolism. It’s found in many types of tissues in various forms called isoenzymes, which differ slightly in properties.
• The researchers observed that most tissues contain three cytoplasmic-originated AST isoenzymes (cAST) with isoelectric points of 5.6, 5.7, and 5.9, and a single mitochondrial-originated isoenzyme (mAST) with an isoelectric point of 9.

Additional Observations and Conclusions

• Serum from horses with azoturia, a condition characterized by the presence of an excessively high concentration of nitrogen compounds in the urine, contained an extra cytoplasmic subform with an isoelectric point of 5.8. The formation of this form couldn’t be induced by ageing, freezing or thawing, or enzyme binding to gamma globulins or lipids.
• When the ratio of cAST to mAST was separated by ion exchange chromatography, it varies widely between tissues, with either cAST not being detectable in the lungs, or mAST not being detectable in the serum.
• The ageing of equine muscle homogenates led to the formation of two artifact subforms with isoelectric points of 6.0 and 6.1.
• Despite the varying ratios of mitochondrial to cytoplasmic AST among different tissues, the researchers concluded that there’s no tissue specificity of either cytoplasmic or mitochondrial isoenzymes. Hence, the examination of the serum wouldn’t provide insight into the source organ.