title: Small molecule functional discrimination of the kinases required for the microbial synthesis of threonine and isoleucine.
abstract: The biosynthesis of l-threonine and l-isoleucine in bacteria and in fungi requires the action of 2 amino acid kinases: aspartate kinase and homoserine kinase. Although these kinases bind similar substrates and catalyze analogous phosphotransfer chemistry, they do not show high amino acid sequence homology. We show that despite this difference, both kinases form a ternary complex consisting of enzyme- adenosine triphosphate- amino acid to accomplish phosphoryl transfer. With this similarity in mind, we set out to identify molecules that could lead to inhibitors with activity against both kinases in the pathway. We synthesized a series of aspartic acid-adenosine bisubstrate compounds separated by a variable length alkyl linker that we hypothesized could bind to these kinases. These bisubstrate compounds only inhibited the bacterial aspartate kinase. These results reveal unexpected differences in small molecule interactions among these functionally similar enzymes.
authors.affiliation: Antimicrobial Research Centre, Department of Biochemistry, McMaster University, 1200 Main Street W., Hamilton, Ontario, Canada L8N 3Z5.
authors.forename: David
authors.initials: D
authors.lastname: Bareich
authors.forename: Kalinka
authors.initials: K
authors.lastname: Koteva
authors.forename: Ishac
authors.initials: I
authors.lastname: Nazi
authors.forename: Gerard D
authors.initials: GD
authors.lastname: Wright
mesh_terms: D000241:Adenosine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D001222:Aspartate Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001224:Aspartic Acid / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002384:Catalysis / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007532:Isoleucine / Q000096:biosynthesis*; D007700:Kinetics; D015394:Molecular Structure; D010766:Phosphorylation / Q000187:drug effects; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D013379:Substrate Specificity; D013912:Threonine / Q000096:biosynthesis*
chemical_list: D004791:Enzyme Inhibitors; D007532:Isoleucine; D013912:Threonine; D001224:Aspartic Acid; D000255:Adenosine Triphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C021370:homoserine kinase; D001222:Aspartate Kinase; D000241:Adenosine