- Additional Attributes: Proteolytic Enzymes
- Donor / Source:Rabbit Muscle
- Molecular Weight:156.8 kDa (Theoretical)
- Extinction Coeff:133,560 cm-1 M-1 (Theoretical)
E1%,280 = 8.52 (Theoretical)
- Isoelectric point:8.47 (Theoretical)
Fructose-biphosphate aldolase (ALD) catalyzes a key reaction in glycolysis and energy production:
Aldolase is present in all animal and plant tissue, and in most microorganisms. Class I aldolase, found in animal and higher plant tissue, is characterized by the lack of requirement for a bivalent metal cofactor, and by the formation of ketimine Schiff base intermediate with the substrate dihyroxyacetone phosphate. Class II aldolase, found only in prokaryotes and lower eukaryotes, requires a bivalent metal cofactor (Heron and Caprioli 1975, London 1974, and Lebherz et al. 1973, Gefflaut et al. 1995). There are three types of Class I aldolases: Type A (the major form) is found in muscle; Type B in liver and kidney; and Type C (plus some A) in brain (Horecker et al. 1972).
Aldolase is highly specific for its substrate, D-fructose.
The three isozymes (A, B, and C) found in mammals are composed of four identical subunits, each a polypeptide chain of 360 amino acids. The enzyme has a homotetrameric structure with subunits that are approximately 40 kDa (Marsh and Lebherz 1992). The structure of these subunits is a beta-barrel, surrounded by alpha-helices and connecting loops (Littlechild and Watson 1993). If activity of one of the four subunits of the homotetramer is knocked out, the entire complex is incapable of normal function, indicating a tight communication between active sites (Marsh and Lebherz 1992).
The primary structures of Class I eukaryotic enzymes are highly conserved (Kelly and Tolan 1986, and Freemont et al. 1988); however, there are no similarities between the sequences of Class I and Class II enzymes, as they have separate evolutionary origins (Marsh and Lebherz 1992). However, both Class I and Class II enzymes contain carboxy-terminal tyrosine residues that are required for maximal catalytic activity (Rutter 1961, and Morse and Horecker 1968). Prolonged contractile activity reduces the type A aldolase expression in mRNA by downregulating cytoplasmic glycolytic enzymes, and enhancing mitochondrial enzymatic activity (Williams et al. 1986).
Protein Accession Number: P00883