Molecular characterization and expression of the equine M(1) and M(2)-pyruvate kinase gene.

This research article presents a study on the molecular properties of certain glycolytic enzymes – equine M(1) and M(2)-pyruvate kinase (PK) – found in horses. This includes investigation of their full-length genetic codes, chromosomal location, and expression in various tissues, with findings indicating they may operate differently from similar enzymes in other mammals.

Extraction and Molecular Characterization

• This research started by isolating and examining genetic materials, specifically messenger ribonucleic acids (mRNAs), from two sources in thoroughbred horses: skeletal muscle and hair roots. These specific mRNAs correspond to the glycolytic enzymes eM(1) and eM(2)-PK.
• The full-length genetic sequences (also known as cDNAs) of both eM(1) and eM(2)-PK were determined, found to consist of 2,320 and 2,376 base pairs (bp) respectively, containing an integral part known as an open reading frame spanning 1,596 bp.
• The researchers located these genetic sequences on the horse’s first chromosome. The overall gene responsible for producing the enzyme, known as the PKM gene, is made up of twelve individual sections or exons.

Further Investigation

• Researchers took a closer look at two particular exons from the eM(1)-PK (exon 9) and eM(2)-PK (exon 10) genes across five different horse species.
• In a chain of 55 amino acids encoded by exon 9, two common residues (Glu 418 and Lys 422) seen in similar enzymes across different vertebrae are substituted by different residues (Gln 418 and His 422).
• The paper reports conservation of transcriptional regulatory elements among the horse species, which have the potential to alter gene expression via a process called alternative splicing.

Expression Analysis

• A technique called semi-quantitative RT-PCR was used to measure the expression of both eM(1) and eM(2)-PK mRNAs in the horse’s skeletal muscle, heart, and brain.
• Interestingly, researchers also discovered that the eM(2)-PK mRNA derived from hair roots had a different transcriptional start site (the beginning point where gene-reading and protein synthesis starts) compared to those from other tissues, and expressed more specifically.

Summary and Implication

• Based on the observations, the researchers propose that both eM(1) and eM(2)-PKs may have unique kinetic properties and transcriptional regulatory mechanisms in horses, which could be different from those seen in other mammals.