Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.1.18 (branching enzyme)
 628 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The amylose content of rice caryopsis is determined by Wx protein, one kind of granule-bound starch synthetase which is encoded by Wx gene. Different rice types and species have different levels of Wx gene expression and have different amylose contents in their caryopsis. Wuyunjing No.7 (2200), the japonica rice with an amylose content 17% and its transgenic rice lines with antisense Wx gene (2201 and 2203, with amylose contents 8.5% and 2% respectively), and Longtefu (LP03), the indica rice with a high amylose content (28%) and its transgenic rice with antisense Wx gene (A199, with an amylose content 9%) were used to investigate the effects of Wx protein content decrease on the activities of enzymes involved in starch synthesis and thereby starch accumulation. The results indicated that with the decrease in Wx protein, the amylose content in transgenic caryopsis was reduced accordingly, whereas the amylopectin content per caryopsis (mg/grain) was not affected, and made the total starch content in transgenic caryopsis markedly lower than their parents. With the development of caryopsis, the amylose/total starch ratio was not changed significantly in the two parent caryopses, LP03 and 2200, but it went down gradually in their transgenic caryopses. The amylose/total starch ratio in transgenic caryopses was very significantly lower than their parents in the same period. The activities of ADP-glucose pyrophosphorylase (ADPG-PPase), granule-bound starch synthase (GBSS), soluble starch synthase (SSS) and starch branching enzyme (SBE) rose rapidly in early periods of grain filling, and soon reached their maximum, then reduced quickly until the middle and later periods of grain filling. Compared with the parents, the GBSS activity in transgenic caryopsis was significantly lowered, and correlated with the amylose reduction. Besides, the maximum activity of GBSS appeared earlier, and the range of the activity was smaller. In transgenic caryopsis, the activities of ADPG-PPase and SSS were higher than their parents in early and middle periods of grain filling, while the SBE activity was higher than their parents in middle and late periods.
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PMID:[Changes in the activities of enzymes involved in starch synthesis and accumulation in caryopsis of transgenic rice with antisense Wx gene]. 1662 21

Amylose, amylopectin and starch dynamic accumulation and key enzymes activities in the grains of 4 maize inbred lines (two high-starch ones and two low-starch ones) were studied. The amounts of amylose, amylopectin and starch in the grains of 4 maize inbred lines increased as sigmoid curves during grain filling period. The changes in amylose, amylopectin and starch accumulation rates followed single-peaked curves, and reached their peaks in the 25-30 days after pollination (DAP). Changes in activities of adenosine diphosphoglucose pyrophosphorylase (ADPG-PPase, EC 2.7.7.27), soluble starch synthase (SSS, EC 2.4.1.21) and starch granule-bound synthase (GBSS, EC 2.4.1.21) in the grains of 4 inbred lines appeared single-peaked curves with the peaks appearing 20-30 DAP. Changes in activities of starch-branching enzyme (Q-enzyme, EC 2.4.1.18) in the grains of high-starch inbred lines appeared single-peaked curves with the peak values at 20 DAP, while the two low-starch inbred lines showed double-peaked curves with the peak values in the 15-20 DAP and 30-35 DAP. There was significant correlation between ADPG-PPase, SSS and GBSS activities. The results indicated that the Q-enzyme had different expression in high- and low-starch maize inbred lines, and verified that ADPG-PPase, SSS and GBSS activities were significantly and positively correlated with amylose, amylopectin and starch accumulation rates.
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PMID:Starch accumulation and activities of key enzymes involved in starch synthesis in the grains of maize inbred lines with different starch contents. 1745 97

The accumulation of glycogen occurs in Escherichia coli and Salmonella enterica serovar Typhimurium as well as in many other bacteria. Glycogen will be formed when there is an excess of carbon under conditions in which growth is limited due to the lack of a growth nutrient, e.g., a nitrogen source. The structural genes of the glycogen biosynthetic enzymes of E. coli and S. serovar Typhimurium have been cloned previously, and that has provided insights in the genetic regulation of glycogen synthesis. An important aspect of the regulation of glycogen synthesis is the allosteric regulation of the ADP-Glc PPase. The current information, views, and concepts regarding the regulation of enzyme activity and the expression of the glycogen biosynthetic enzymes are presented in this review. The recent information on the amino acid residues critical for the activity of both glycogen synthase and branching enzyme (BE) is also presented. The residue involved in catalysis in the E. coli ADP-Glc PPase was determined by comparing a predicted structure of the enzyme with the known three-dimensional structures of sugar-nucleotide PPase domains. The molecular cloning of the E. coliglg K-12 structural genes greatly facilitated the subsequent study of the genetic regulation of bacterial glycogen biosynthesis. Results from studies of glycogen excess E. coli B mutants SG3 and AC70R1, which exhibit enhanced levels of the enzymes in the glycogen synthesis pathway (i.e., they are derepressed mutants), suggested that glycogen synthesis is under negative genetic regulation.
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PMID:Glycogen: Biosynthesis and Regulation. 2644 53