P. Rellos et al., Expression, purification, and characterization of natural mutants of humanaldolase B - Role of quaternary structure in catalysis, J BIOL CHEM, 275(2), 2000, pp. 1145-1151
Fructaldolases (EC 4.1.2.13) are ancient enzymes of glycolysis that catalyz
e the reversible cleavage of phosphofructose esters into cognate triose (ph
osphates). Three vertebrate isozymes of Class I aldolase have arisen by gen
e duplication and display distinct activity profiles with fructose 1,6-bisp
hosphate and with fructose l-phosphate, We describe the biochemical and bio
physical characterization of seven natural human aldolase B variants, ident
ified in patients suffering from hereditary fructose intolerance and expres
sed as recombinant proteins in E, call, from which they were purified to ho
mogeneity. The mutant aldolases were all missense variants and could be cla
ssified into two principal groups: catalytic mutants, with retained tetrame
ric structure but altered kinetic properties (W147R, R303W, and A337V), and
structural mutants, in which the homotetramers readily dissociate into sub
units with greatly impaired enzymatic activity (A149P, A174D, L256P, and N3
34K), Investigation of these two classes of mutant enzyme suggests that the
integrity of the quaternary structure of aldolase B is critical for mainta
ining its full catalytic function.