Aldolase A (ALDOA, or ALDA), also known as fructose-bisphosphate aldolase, is an enzyme that in humans is encoded by the ALDOA gene on chromosome 16. The protein encoded by this gene is a glycolytic enzyme that catalyzes the reversible conversion of fructose-1,6-bisphosphate to glyceraldehyde 3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). Three aldolase isozymes (A, B, and C), encoded by three different genes, are differentially expressed during development. Aldolase A is found in the developing embryo and is produced in even greater amounts in adult muscle. Aldolase A expression is repressed in adult liver, kidney and intestine and similar to aldolase C levels in brain and other nervous tissue. Aldolase A deficiency has been associated with myopathy and hemolytic anemia. Alternative splicing and alternative promoter usage results in multiple transcript variants. Related pseudogenes have been identified on chromosomes 3 and 10. [provided by RefSeq, Aug 2011] Structure ALDOA is a homotetramer and one of the three aldolase isozymes (A, B, and C), encoded by three different genes. The ALDOA gene contains 8 exons and the 5' UTR IB. Key amino acids responsible for its catalytic function have been identified. The residue Tyr363 functions as the acid–base catalyst for protonating C3 of the substrate, while Lys146 is proposed to stabilize the negative charge of the resulting conjugate base of Tyr363 and the strained configuration of the C-terminal. Residue Glu187 participates in multiple functions, including FBP aldolase catalysis, acid–base catalysis during substrate binding, dehydration, and substrate cleavage. Though ALDOA localizes to the nucleus, it lacks any known nuclear localization signals (NLS). Mechanism In mammalian aldolase, the key catalytic amino acid residues involved in the reaction are lysine and tyrosine. The tyrosine acts as an efficient hydrogen acceptor while the lysine covalently binds and stabilizes the intermediates. Many bacteria use two magnesium ions in place of the lysine. The numbering of the carbon atoms indicates the fate of the carbons according to their position in fructose 6-phosphate. Function ALDOA is a key enzyme in the fourth step of glycolysis, as well as in the reverse pathway gluconeogenesis. It catalyzes the reversible conversion of fructose-1,6-bisphosphate to glyceraldehydes-3-phosphate and dihydroxyacetone phosphate by aldol cleavage of the C3–C4 bond. As a result, it is a crucial player in ATP biosynthesis. ALDOA also contributes to other "moonlighting" functions such as muscle maintenance, regulation of cell shape and motility, striated muscle contraction, actin cytoskeleton organization, and regulation of cell