Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tissue distribution and activity of enzymes involved in sucrose and hexose metabolism were examined in kernels of two inbreds of maize (Zea mays L.) at progressive stages of development. Levels of sugars and starch were also quantitated throughout development. Enzyme activities studied were: ATP-linked fructokinase, UTP-linked fructokinase, ATP-linked glucokinase, sucrose synthase, UDP-Glc pyrophosphorylase, UDP-Glc dehydrogenase, PPi-linked phosphofructokinase, ATP-linked phosphofructokinase, NAD-dependent sorbitol dehydrogenase, NADP-dependent 6-P-gluconate dehydrogenase, NADP-dependent Glc-6-P dehydrogenase, aldolase, phosphoglucoisomerase, and phosphoglucomutase. Distribution of invertase activity was examined histochemically. Hexokinase and ATP-linked phosphofructokinase activities were the lowest among these enzymes and it is likely that these enzymes may regulate the utilization of sucrose in developing maize kernels. Most of the hexokinase activity was found in the endosperm, but the embryo had high activity on a dry weight basis. The endosperm, which stores primarily starch, contained high PPi-linked phosphofructokinase and low ATP-linked phosphofructokinase activities, whereas the embryo, which stores primarily lipids, had much higher ATP-linked phosphofructokinase activity than did the endosperm. It is suggested that PPi required by UDP-Glc pyrophosphorylase and PPi-linked phosphofructokinase in the endosperm may be supplied by starch synthesis. Sorbitol dehydrogenase activity was largely restricted to the endosperm, whereas 6-P-gluconate and Glc-6-P dehydrogenase activities were highest in the base and pericarp. A possible metabolic pathway by which sucrose is converted into starch is proposed.
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PMID:Enzymes of sucrose and hexose metabolism in developing kernels of two inbreds of maize. 1666 24

Sorbitol and sucrose are major products of photosynthesis distributed in apple trees (Malus domestica Borkh. cv. "Greensleeves") that affect quality in fruit. Transgenic apple plants were silenced or up-regulated for sorbitol-6-phosphate dehydrogenase by using the CaMV35S promoter to define the role of sorbitol distribution in fruit development. Transgenic plants with suppressed sorbitol-6-phosphate dehydrogenase compensated by accumulating sucrose and starch in leaves, and morning and midday net carbon assimilation rates were significantly lower. The sorbitol to sucrose ratio in leaves was reduced by approximately 90% and in phloem exudates by approximately 75%. The fruit accumulated more glucose and less fructose, starch, and malic acid, with no overall differences in weight and firmness. Sorbitol dehydrogenase activity was reduced in silenced fruit, but activities of neutral invertase, vacuolar invertase, cell wall-bound invertase, fructose kinase, and hexokinase were unaffected. Analyses of transcript levels and activity of enzymes involved in carbohydrate metabolism throughout fruit development revealed significant differences in pathways related to sorbitol transport and breakdown. Together, these results suggest that sorbitol distribution plays a key role in fruit carbon metabolism and affects quality attributes such as sugar-acid balance and starch accumulation.
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PMID:Silencing leaf sorbitol synthesis alters long-distance partitioning and apple fruit quality. 1713 42