Glucokinase is one of the four hexokinases present in mammalian tissues. It is expressed in two cell types that have to respond to changes in the blood glucose concentration, the liver parenchymal cell and the β‐cells of pancreatic islets. The former are responsible for the metabolism and storage of an important part of the ingested glucose, whereas the latter secrete insulin in response to an increase in the blood glucose level. One major characteristic of glucokinase is that it has a relatively low affinity for glucose and displays positive cooperativity for this substrate, despite the fact that it is a monometic enzyme. Furthermore, unlike other hexokinases, it is not inhibited by micromolar (physiological) concentrations of glucose 6‐phosphate but by a regulatory protein that transduces the effect of fructose 6‐phosphate and of fructose 1‐phosphate. The purpose of this review is to describe these aspects of the regulation of glucokinase.— Van Schaftingen, E., Detheux, M., Veiga da Cunha, M. Short‐term control of glucokinase activity; role of a regulatory protein. FASEB J. 8: 414‐419; 1994.

Tracking the within-patient evolution of SARS-CoV-2 is key to understanding how this pandemic virus shapes its genome toward immune evasion and survival. In the present study, by monitoring a long-term COVID-19 immunocompromised patient, we observed the concurrent emergence of mutations potentially associated with immune evasion and/or enhanced transmission, mostly targeting the SARS-CoV-2 key host-interacting protein and antigen.

The simultaneous fermentation of glycerol and sugar by Lactobaillus brevis B22 and Lactobacillus buchneri B190 increases both the growth rate and total growth. The reduction of glycerol to 1,3-propanediol by the lactobacilli was found to influence the metabolism of the sugar cofermented by channelling some of the intermediate metabolites (e.g., pyruvate) towards NADH-producing (rather than NADH-consuming) reactions. Ultimately, the absolute requirement for NADH to prevent the accumulation of 3-hydroxypropionaldehyde leads to a novel lactate-glycerol cofermentation. As a result, additional ATP can be made not only by (i) converting pyruvate to acetate via acetyl phosphate rather than to the ethanol usually found and (ii) oxidizing part of the intermediate pyruvate to acetate instead of the usual reduction to lactate but also by (iii) reoxidation of accumulated lactate to acetate via pyruvate. The conversion of lactate to pyruvate is probably catalyzed by NAD-independent lactate dehydrogenases that are found only in the cultures oxidizing lactate and producing 1,3-propanediol, suggesting a correlation between the expression of these enzymes and a raised intracellular NAD/NADH ratio. The enzymes metabolizing glycerol (glycerol dehydratase and 1,3-propanediol dehydrogenase) were expressed in concert without necessary induction by added glycerol, although their expression may also be influenced by the intracellular NAD/NADH ratio set by the different carbohydrates fermented.A few strains of lactobacilli have the ability to produce 1,3-propanediol (1,3-PDL) from glycerol while metabolizing glucose or fructose (18,23,25). These bacteria all have a coenzyme B12-dependent dehydratase responsible for the dehydration of glycerol to 3-hydroxypropionaldehyde (3-HPA), which is subsequently reduced by NADH to 1,3-PDL (19,22,27). Since glycerol is not metabolized as a sole energy source, its cofermentation with sugar was reported to affect the metabolism of glucose or fructose (but not of ribose) exclusively by reoxidizing NADH equivalent to that formed during the catabolism of the sugar via the 6-phosphogluconate pathway. Work with growing cultures by Schutz and Radler (18) supported this idea; by suppressing ethanol formation, glycerol allowed greater acetate production, the extra carbon flow through acetyl phosphate leading to consistently better growth of lactobacilli.However, the metabolite balances obtained by these investigators show an unexplained disparity between the glucose used and the lactate and acetate plus ethanol formed and suggested to us a more complex effect of glycerol in the metabolism of glucose. In the present study a further investigation of this problem shows that, for Lactobacillus brevis B22 and Lactobacillus buchneri B190 growing with glycerol and growth-limiting concentrations of sugar, 1,3-PDL is not produced exclusively during growth with substrates metabolized via the 6-phosphogluconate pathway. Thus, glycerol reduction does not depend only on the necessity to recycle the NADH formed during the ...

No abstract