THE ENOLASES OF ICE PLANT AND ARABIDOPSIS CONTAIN A POTENTIAL DISULFIDE AND ARE REDOX-SENSITIVE

The simulated structures of the enolases of Arabidopsis and the common ice plant contain a pair of Cys residues in the correct orientation t o form a disulphide bond. Formation of this disulphide might be expect ed to affect the positioning of several residues in the active site. T he enzyme in crude extracts of these two plants is activated by oxidat ion. Apparently formation of the disulphide crosslink enhances catalys is. The enolases from tomato leaves, maize roots and castor bean embry os lack one of these Cys residues and are not redox sensitive. It seem s possible that enolase is redox-regulated by a cytosolic thioredoxin system in a limited number of plant species including ice plant and Ar abidopsis. (C) 1998 Elsevier Science Ltd. All rights reserved.