The cytosolic fructose bisphosphatase of Brassica napus contains a new potential regulatory disulfide and is redox-sensitive

Abstract

The deduced amino acid sequences of the Brassica napus and sugar cane ( Saccharum sp.) cytosolic fructose bisphosphatases (EC 3.1.3.11) have appeared recently. When the three-dimensional structure of the Brassica napus bisphosphatase was modeled residue 92, previously identified as a potential redox-sensitive regulatory cysteine in the cytosolic enzymes from potato, sugarbeet and spinach [L.E. Anderson, et al., Planta 196 (1995) 118–124], was a serine. (Numbering according to Protein Data Bank entry 4FBP.) Instead there is a Cys at position 110, close enough to Cys-114, the second member of the potential regulatory cysteine pair in the other cytosolic fructose bisphosphatases, to suggest the possibility of disulfide bond formation and the enzyme is redox-sensitive. The sugar cane enzyme, like the other three cytosolic fructose bisphosphatases, contains Cys-92 and Cys-114. It also is redox-sensitive. Apparently a disulfide anywhere in the region of Cys-114, -92 and -110 can function in the redox-modulation of the activity of this enzyme.