Evidence that fructose 1,6-bisphosphate specifically protects the alpha-subunit of pyrophosphate-dependent 6-phosphofructo-1-phosphotransferase against proteolytic degradation.
Pyrophosphate-dependent 6-phosphofructo-1-phosphotransferase (PFP) consists of alpha (regulatory) and beta (catalytic) subunits. The alpha-subunit was previously reported to be much more susceptible to tryptic digestion than the beta-subunit. In this study, ligand-induced protection of PFP subunits against proteolysis by subtilisin was investigated in vitro and the data obtained demonstrated that fructose 1,6-bisphosphate (Fru-1,6-P(2)), while exerting negligible effect on the beta-subunit, remarkably protected the alpha-subunit against proteolytic degradation. Western blot analysis revealed a good correlation between the Fru-1,6-P(2) concentration and the degree of corresponding protection on the alpha-subunit against proteolysis. In contrast, none of other examined ligands including fructose 2,6-bisphosphate, fructose 6-phosphate and pyrophosphate had such protection on the alpha-subunit. This finding (1) indicates that the stability of the alpha-subunit can be selectively increased by Fru-1,6-P(2), and (2) suggests that Fru-1,6-P(2) is likely a special effector of the alpha-subunit.
Wang
Y H
YH
Shanghai Institute of Plant Physiology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, PR China. yhwang@iris.sipp.ac.cn
Shi
J N
JN
D004591:Electrophoresis, Polyacrylamide Gel; D005635:Fructosediphosphates / Q000378:metabolism* / Q000494:pharmacology; D008024:Ligands; D010770:Phosphotransferases / Q000378:metabolism*; D011198:Solanum tuberosum / Q000201:enzymology; D020860:Subtilisin / Q000037:antagonists & inhibitors / Q000378:metabolism
D005635:Fructosediphosphates; D008024:Ligands; D010770:Phosphotransferases; C022502:pyrophosphate-fructose 6-phosphate 1-phosphotransferase; D020860:Subtilisin; C029063:fructose-1,6-diphosphate