Structural highlights
FunctionHXKG_YEAST Two isoenzymes, hexokinase-1 and hexokinase-2, can phosphorylate keto- and aldohexoses in yeast, whereas a third isoenzyme, GLK, is specific for aldohexoses. All glucose phosphorylating enzymes are involved in glucose uptake.[1] Publication Abstract from PubMedThe actin fold is found in cytoskeletal polymers, chaperones, and various metabolic enzymes. Many actin-fold proteins, such as the carbohydrate kinases, do not polymerize. We found that Glk1, a Saccharomyces cerevisiae glucokinase, forms two-stranded filaments with ultrastructure that is distinct from that of cytoskeletal polymers. In cells, Glk1 polymerized upon sugar addition and depolymerized upon sugar withdrawal. Polymerization inhibits enzymatic activity; the Glk1 monomer-polymer equilibrium sets a maximum rate of glucose phosphorylation regardless of Glk1 concentration. A mutation that eliminated Glk1 polymerization alleviated concentration-dependent enzyme inhibition. Yeast containing nonpolymerizing Glk1 were less fit when growing on sugars and more likely to die when refed glucose. Glk1 polymerization arose independently from other actin-related filaments and may allow yeast to rapidly modulate glucokinase activity as nutrient availability changes. Polymerization in the actin ATPase clan regulates hexokinase activity in yeast.,Stoddard PR, Lynch EM, Farrell DP, Dosey AM, DiMaio F, Williams TA, Kollman JM, Murray AW, Garner EC Science. 2020 Feb 28;367(6481):1039-1042. doi: 10.1126/science.aay5359. PMID:32108112[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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