Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.2.13 (aldolase)
 3,461 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

Sugar metabolism in kernels of starch-deficient endosperm mutants of maize (Zea mays L.) was examined to determine how single locus mutations of carbohydrate metabolism affect carbohydrate metabolism as a whole. Activities of 14 enyzmes were measured in extracts from endosperms from isogenic lines of normal, shrunken, shrunken-2, shrunken-4, brittle-1, and brittle-2 maize in an OH43 background. Nearly every enzyme activity examined was affected in some or all of the mutants. Sucrose synthase and aldolase activities were lower in all mutants compared to normal. ADP-Glc pyrophosphorylase activity in immature kernels was much higher in brittle endosperms than in normal, but absent in brittle-2 and shrunken-2 endosperms. The activity in those genotypes exhibiting activity was positively correlated with sucrose concentration in the kernels. Sucrose may be modulating the coarse control of ADP-Glc pyrophosphorylase activity by affecting the genetic transcription of message for this enzyme. Sorbitol dehydrogenase activity was negatively correlated with its substrate, fructose, supporting the hypothesis that sorbitol dehydrogenase converts fructose produced during sucrose degradation into sorbitol. Glucokinase activity was positively correlated with mature kernel dry weight. This supports the hypothesis that glucokinase activity may limit sucrose utilization. Shrunken-4 extracts had lower activities for a number of enzymes, supporting the view that this mutant may have an impediment to protein synthesis. Elevated sucrose levels were evenly distributed throughout 20-day postpollination shrunken-2 kernels, whereas a sucrose concentration gradient existed in normal kernels between the basal region and the upper endosperm. This gradient is apparently generated by the utilization of sugars and may facilitate the movement of sugars into developing corn kernels.
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PMID:Sugar metabolism in developing kernels of starch-deficient endosperm mutants of maize. 1666 16