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Hexokinase Isoenzyme (hexokinase + isoenzyme)
Selected AbstractsFunctional analysis of Drosophila melanogaster hexokinase Hex-A locus: multiple Initiator-like elements enhance DPE containing promoter activityINSECT MOLECULAR BIOLOGY, Issue 1 2007P. C. Jayakumar Abstract Flight muscle Hexokinase-A (HEX-A) is the most conserved and essential hexokinase isoenzyme among Drosophila species. In this study, the Hex-A locus, encoding the HEX-A isoenzyme, has been analysed for the elements regulating its expression. By sequencing the 5, ends of Hex-A cDNA amplified by 5, RACE, we identified a transcription start site that overlapped the Initiator and downstream promoter elements. A 214 bp sequence, encompassing transcription start sites and promoter elements, was required for minimal promoter activity. DNA sequence to the 5, end of the minimal promoter element did not demonstrate any promoter activity; however, its inclusion with the basal promoter element enhanced the promoter activity. Oligonucleotide competition and site-directed mutagenesis identified the Initiator-like sequences, TCAWT, present in this region that were responsible for enhancing the promoter activity. The Hex-A locus is expressed as a single protein in Drosophila cell line, whereas in pupae, larvae and adult flies, it is expressed as two distinct types. [source] Activities of glucose phosphorylation, glucose-6-phosphatase and lipogenic enzymes in the liver of perch, Perca fluviatilis, after different dietary treatmentAQUACULTURE RESEARCH, Issue 2001B Borrebaek Abstract Glucose phosphorylation was increased and the activity of glucose-6-phosphatase was decreased in the liver of perch Perca fluviatilis after feeding previously fasted fish with a high protein/low carbohydrate diet as well as with a diet containing 23% carbohydrate. Activity of the low affinity hexokinase IV (or D), also called glucokinase (GK), was not observed in the liver of perch on the natural diet, fasted perch or perch after feeding with the high protein/low-carbohydrate diet (< 0.2% CHO). How ever, hepatic GK-activity appeared after feeding with the carbohydrate containing diet. By contrast, the activity of hepatic high affinity hexokinase (HK), which was very low in fasted fish, was strongly increased after feeding with the low-carbohydrate as well as the carbohydrate-containing diet. Apparently, HK rather than GK is the hexokinase isoenzyme that is consistently regulated inversely to glucose-6-phosphatase. Activities of the lipogenic enzymes glucose-6-phosphate dehydrogenase, ATP-citrate lyase and malic enzyme were increased by feeding, particularly with the high protein/low carbohydrate diet. Very high levels of hepatic glycogen were observed after both diets. The results are in accordance with the hypothesis that the hepatic high affinity isoenzyme (HK) has a particular anabolic role. [source] Impaired enzyme-to-enzyme channelling between hexokinase isoenzyme(s) and phosphoglucoisomerase in rat pancreatic islets incubated at a low concentration of D -glucoseCELL BIOCHEMISTRY AND FUNCTION, Issue 1 2005Ying Zhang Abstract It was recently proposed that in rat pancreatic islets exposed to 8.3,mMD -glucose, ,- D -glucose-6-phosphate undergoes enzyme-to-enzyme channelling between hexokinase isoenzyme(s) and phosphoglucoisomerase. To explore the identity of the hexokinase isoenzyme(s) involved in such a tunnelling process, the generation of 3HOH from the ,- and ,-anomers of either D -[2- 3H]glucose or D -[5- 3H]glucose was now measured over 60,min incubation at 4°C in pancreatic islets exposed only to 2.8,mMD -glucose, in order to decrease the relative contribution of glucokinase to the phosphorylation of the hexose. Under these experimental conditions, the ratio for 3HOH production from D -[2- 3H]glucose/D -[5- 3H]glucose at anomeric equilibrium (39.7,±,11.6%) and the ,/, ratios for the generation of 3HOH from either the D -[2- 3H]glucose anomers (70.9,±,12.6%) or the D -[5- 3H]glucose anomers (59.6,±,12.4%) indicated that a much greater fraction of ,- D -glucose-6-phosphate escapes from the process of enzyme-to-enzyme channelling in the islets exposed to 2.8,mM, rather than 8.3,mMD -glucose. These findings suggest, therefore, that the postulated process of enzyme-to-enzyme channelling involves mainly glucokinase. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||