THE CYTOSOLIC FRUCTOSE BISPHOSPHATASE OF BRASSICA-NAPUS CONTAINS A NEW POTENTIAL REGULATORY DISULFIDE AND IS REDOX-SENSITIVE

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 Brassic a napus bisphosphatase was modeled residue 92, previously identified a s a potential redox-sensitive regulatory cysteine in the cytosolic enz ymes from potato, sugarbeet and spinach [L.E. Anderson, et al., Planta 196 (1995) 118-124], was a serine. (Numbering according to Protein Da ta Bank entry 4FBP.) Instead there is a Cys at position 110, close eno ugh 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-sensit ive. The sugar cane enzyme, like the other three cytosolic fructose bi sphosphatases, contains Cys-92 and Cys-114. It also is redox-sensitive . Apparently a disulfide anywhere in the region of Cys-114, -92 and -1 10 can function in the redox-modulation of the activity of this enzyme . (C) 1997 Elsevier Science Ireland Ltd.