Characterization, by the binding of D-mannonolactone, of the subsites adjacent to the catalytic site of glucoamylase from Rhizopus niveus

Contributions of Dexter French (1918-1981) to cycloamylose/cyclodextrin and starch science

Professor Dexter French (1918-1981) was an American chemist and biochemist at Iowa State College (University in 1959). He devoted his career to advance knowledge of polysaccharides and oligosaccharides, in particular starch, cyclodextrins, and enzymes. Cyclodextrins are oligosaccharides obtained from starch and are typically cage molecules with a hydrophobic cavity that can encapsulate other compounds nowadays the basis for many industrial applications. Since the 1960s, he has been recognized as an outstanding authority in the field of starches and cyclodextrins and has inspired researchers in laboratories around the world. This review, on the fortieth anniversary of his death, commemorates his remarkable contribution to starch and cyclodextrin chemistry. Firstly, we give an overview of his personal life and career. Secondly, we highlight some of the results on starch and cyclodextrins from Professor French and his group. A third part discusses his impact on the modern chemistry of cyclodextrins and starch.

Binding of isomaltose and maltose to the glucoamylase from Aspergillus niger, as studied by fluorescence spectrophotometry and steady-state kinetics

The binding of maltose, isomaltose, and D-glucono-1,5-lactone to the glucoamylase [E.C.3.2.1.3] from Aspergillus niger was monitored by the fluorescence-intensity change (delta F) based on the tryptophan residues of the enzyme, and the binding parameters (Kd and delta Fmax) were evaluated from the dependence of delta F on the concentration of substrate and analogue. Maltose caused the fluorescence-intensity change, but isomaltose did not, although it is hydrolyzed by the enzyme. Both substrates bind to the glucoamylase of Rhizopus niveus and cause delta F, suggesting that some difference exists in the conformation of the isomaltose-binding subsites between the two glucoamylases.