TY - JOUR
T1 - Relationship between thiol group modification and the binding site for fructose 2,6-bisphosphate on rabbit liver fructose-1,6-bisphosphatase
AU - Liu, F.
AU - Fromm, H. J.
N1 - Copyright:
Copyright 2004 Elsevier B.V., All rights reserved.
PY - 1988
Y1 - 1988
N2 - A thiol group present in rabbit liver fructose-1,6-bisphosphatase is capable of reacting rapidly with N-ethylmaleimide (NEM) with a stoichiometry of one per monomer. Either fructose 1,6-bisphosphatase or fructose 2,6-bisphosphate at 500 μM protected against the loss of fructose 2,6 bisphosphate inhibition potential when fructose-1 2,6-bisphosphatase was treated with NEM in the presence of AMP for up to 20 min. Fructose 2,6-bisphosphate proved more effective than fructose 1,6-bisphosphate when fructose-1,6-bisphosphatase was treated with NEM for 90-120 min. The NEM-modified enzyme exhibited a significant loss of catalytic activity. Fructose 2,6-bisphosphatase was more effective than the substrate in protecting against the thiol group modification when the ligands are present with the enzyme and NEM. 100 μM fructose 2,6-bisphosphate, a level that should almost saturate the inhibitory binding site of the enzyme under our experimental conditions, affords only partial protection against the loss of activity of the enzyme caused by the NEM modification. In addition, the inhibition pattern for fructose 2,6-bisphosphate of the NEM-derivatized enzyme was found to be linear competitive, identical to the type of inhibition observed with the native enzyme. The K(D) for the modified enzyme was significantly greater than that of untreated fructose-1,6-bisphosphatase. Examination of space-filling models of the two bisphosphates suggest that they are very similar in conformation. On the basis of these observations, we suggest that fructose 1,6-bisphosphatase and fructose 2,6-bisphosphate occupy overlapping sites within the active site domain of fructose-1,6-bisphosphatase. Fructose 2,6-bisphosphate affords better shielding against thiol-NEM modification than fructose 1,6-bisphosphate; however, the difference between the two ligands is quantitative rather than qualitative.
AB - A thiol group present in rabbit liver fructose-1,6-bisphosphatase is capable of reacting rapidly with N-ethylmaleimide (NEM) with a stoichiometry of one per monomer. Either fructose 1,6-bisphosphatase or fructose 2,6-bisphosphate at 500 μM protected against the loss of fructose 2,6 bisphosphate inhibition potential when fructose-1 2,6-bisphosphatase was treated with NEM in the presence of AMP for up to 20 min. Fructose 2,6-bisphosphate proved more effective than fructose 1,6-bisphosphate when fructose-1,6-bisphosphatase was treated with NEM for 90-120 min. The NEM-modified enzyme exhibited a significant loss of catalytic activity. Fructose 2,6-bisphosphatase was more effective than the substrate in protecting against the thiol group modification when the ligands are present with the enzyme and NEM. 100 μM fructose 2,6-bisphosphate, a level that should almost saturate the inhibitory binding site of the enzyme under our experimental conditions, affords only partial protection against the loss of activity of the enzyme caused by the NEM modification. In addition, the inhibition pattern for fructose 2,6-bisphosphate of the NEM-derivatized enzyme was found to be linear competitive, identical to the type of inhibition observed with the native enzyme. The K(D) for the modified enzyme was significantly greater than that of untreated fructose-1,6-bisphosphatase. Examination of space-filling models of the two bisphosphates suggest that they are very similar in conformation. On the basis of these observations, we suggest that fructose 1,6-bisphosphatase and fructose 2,6-bisphosphate occupy overlapping sites within the active site domain of fructose-1,6-bisphosphatase. Fructose 2,6-bisphosphate affords better shielding against thiol-NEM modification than fructose 1,6-bisphosphate; however, the difference between the two ligands is quantitative rather than qualitative.
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M3 - Article
C2 - 2838468
AN - SCOPUS:0023747292
VL - 263
SP - 10035
EP - 10039
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 20
ER -