Isozymes of plant hexokinase: occurrence, properties and functions.
Hexokinase (HK) occurs in all phyla, as an enzyme of the glycolytic pathway. Its importance in plant metabolism has emerged with compelling evidence that its preferential substrate, glucose, is both a nutrient and a signal molecule that controls development and expression of different classes of genes. A variety of plant tissues and organs have been shown to express multiple HK isoforms with different kinetic properties and subcellular localizations. Although plant HK is known to fulfill a catalytic function and act as a glucose sensor, the physiological relevance of plural isoforms and their contribution to either function are still poorly understood. We review here the current knowledge and hypotheses on the physiological roles of plant HK isoforms that have been identified and characterized. Recent findings provide hints on how the expression patterns, biochemical properties and subcellular localizations of HK isoforms may relate to their modes of action. Special attention is devoted to kinetic, mutant and transgenic data on HKs from Arabidopsis thaliana and the Solanaceae potato, tobacco, and tomato, as well as HK gene expression data from Arabidopsis public DNA microarray resources. Similarities and differences to known properties of animal and yeast HKs are also discussed as they may help to gain further insight into the functional adaptations of plant HKs.
Claeyssen
Eric
E
Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Rue Sherbrooke est, Montréal, Que., Canada H1X 2B2.
Rivoal
Jean
J
D000595:Amino Acid Sequence; D050260:Carbohydrate Metabolism; D020869:Gene Expression Profiling; D006593:Hexokinase / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D007527:Isoenzymes; D010940:Plant Proteins; D006593:Hexokinase