Triose phosphate isomerase
Genbank search results

Triosephosphate isomerase (TIM) is one of the enzymes involved in glycolysis. It is found in a wide variety of organisms, since most organisms perform glycolysis. It catalyses the interconversion of dihydroxyacetone phosphate and glyceraldehyde-3-phosphate (see Fig. 1). This effectively enables a doubling of the yield from the glycolysis of a single glucose molecule.

Figure 1. The catalytic action of triosephosphate isomerase (TIM)

TIM occurs as a dimer, with two identical barrel shaped chains. This can be seen in the Rasmol image of yeast TIM (MMDB Id: 2490, PDB Id: 1YPI).

Biologists use the way in which sequence similarity of a certain protein among different organisms to hypothesize evolutionary branching. The proetin is thus used as a "molecular clock". TIM is a good choice for such an analysis since it is found in organisms of all varieties. We shall now attempt to do such an analysis for the five genome organisms, TIM as our "molecular clock". The appropriate GenBank entries are as follows:

Organism Amino acid sequence? Nucleotide sequence?
Homo sapiens Yes Yes, cDNA
Saccharomyces cerevisiae Yes Yes, whole gene
Mus musculus Yes Yes, mRNA
Drosophila melanogaster Yes Yes, whole gene
Caenorhabditis elegans Yes Yes, whole gene
The above sequences were analyzed for sequence similarity using the MacDNA program, and the results of the analysis can be found here.

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