Kinetic and regulatory properties of HK I(+), a modified form of the type I isozyme of mammalian hexokinase in which interactions between the N- and C-terminal halves have been disrupted.
A modified form (HK I(+)) of rat Type I hexokinase (HK I) has been expressed. HK I(+) contains a centrally located polyalanine insert which, along with the known helical propensity of adjacent sequence, was expected to lead to alpha-helix formation, with resulting distension of the molecule and disruption of interactions between the N- and C-terminal halves. The properties of HK I(+) are consistent with this expectation and with previous proposals that (1) inhibition of HK I by Glc-6-P or its analogs and antagonism of this inhibition by P(i) result from competition of these ligands for a binding site in the N-terminal half of HK I, with resulting conformational changes propagated through interactions with the catalytic C-terminal half, and (2) binding of Glc-6-P to a site in the C-terminal half of HK I is obstructed by interactions between the halves, present in HK I but not HK I(+).
Hashimoto
Mitsuru
M
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
Wilson
John E
JE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D006224:Cricetinae; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006593:Hexokinase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006600:Hexosephosphates / Q000037:antagonists & inhibitors; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010455:Peptides / Q000235:genetics; D010710:Phosphates / Q000494:pharmacology; D017354:Point Mutation; D017433:Protein Structure, Secondary; D014357:Trypsin / Q000737:chemistry
D004791:Enzyme Inhibitors; D006600:Hexosephosphates; D007527:Isoenzymes; D010455:Peptides; D010710:Phosphates; C000096:1,5-anhydroglucitol-6-phosphate; C019529:polyalanine; D006593:Hexokinase; D014357:Trypsin