The<unk>  enzyme catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate; this is the ninth step in glycolysis.<unk>  is a dimeric protein formed from three subunits, α, β, and γ, encoded by different genes. The αα homodimer assumes all<unk>  activity in the early stages of embryo development and in some adult tissues. In tissues that need large amounts of energy, the αγ and γγ in the brain, and αβ and ββ in striated muscles these forms of<unk>  are present. At all stages of development, β-enolase expression is only found in striated muscles. In adult humans, the ββ homodimer accounts for more than 90% of total<unk>  activity in muscle. Two mutations in the ENO3 gene, the gene encoding β-enolase, is responsible for the deficiency, both mutations changed highly conserved amino acid residues. One of the changes was of a glycine residue at position 374 to aspartate, this amino acid change was located in close proximity to the His residue of human<unk> , which is an important part of the β-enolase catalytic site, while the glycine at position 156 changed to glutamate, which may have brought about change the secondary structure of the enzyme. These mutations may impair activity by significantly reducing the steady- state level of the protein, rather than produce a non- functional mutant protein. Mutations of the β-enolase dimer complexes might result in incorrect folding and increased susceptibility to protein degradation thus causing the deficiency. Similar mutations on yeast showed destabilization of the protein and decreased substrate affinity. Destabilization of the protein results in partial dissociation, some researchers propose that in muscle cells this dissociation may be perceived as an abnormality leading to degradation of the mutated<unk> .
Enolase deficiency
Glutaminase deficiency
Aldolase A deficiency
Transaldolase deficiency
Pyruvate kinase deficiency
Ornithine aminotransferase deficiency
Hexokinase deficiency
Malonyl-CoA decarboxylase deficiency