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Glycolysis and Fermentation
Published in Jean-Louis Burgot, Thermodynamics in Bioenergetics, 2019
Fructose and galactose can enter into the glycolytic chain. fructose enters into glycolytic chain through the formation of fructose-1-phosphate with the aid of fructokinase. Then, the fructose-1-phosphate is cut into two parts: the glyceraldehyde plus the dihydroxyacetonephosphate. Here, again, there is a cleavage by retroaldolisation catalysed by a specific fructose-1-phosphate aldolase. The glyceraldehyde is then phosphorylated in glyceraldehyde-3-phosphate by a triose kinase. Hence, it can enter into the glycolysis: galactose enters through the glycolysis chain once it is transformed into glucose-6-phosphate by a process in four steps. There is first the transformation galactose → galactose-1-phosphate: galactose + ATP→galactokinasegalactose-1-phosphate + ADP + H+Secondly, the galactose-1-phosphate reacts with the uridine diphospho-glucose (UDP-glucose) and gives the UDP-galactose and the glucose-1-phosphate. The reaction is catalyzed by the galactose-1-phosphate uridyl transferase. Transformation of galactose-1-phosphate into glucose-1-phosphate.
Potential of “coalho” cheese whey as lactose source for β-galactosidase and ethanol co-production by Kluyveromyces spp. yeasts
Published in Preparative Biochemistry & Biotechnology, 2020
Catherine Teixeira de Carvalho, Sérgio Dantas de Oliveira Júnior, Wildson Bernardino de Brito Lima, Fábio Gonçalves Macêdo de Medeiros, Ana Laura Oliveira de Sá Leitão, Everaldo Silvino dos Santos, Gorete Ribeiro de Macedo, Francisco Caninde de Sousa Júnior
The genes LAC12 and LAC4 are found in the strain K. lactis NRRL Y-8279, and they are responsible for the codification of lactose-permease and ß-galactosidade enzymes, respectively, which play different roles in this process. Lactose-permease enzymes promote the lactose transport through the plasma membrane into the yeast cells, while the β-gal is responsible for the hydrolysis of lactose (disaccharide) into two monosaccharides, glucose and galactose. These two sugars are metabolized via glycolysis, however, before attending this metabolic route, galactose is converted into a glycolytic intermediate, the glucose-6-phosphate, via the Leloir pathway, by the action of three enzymes galactokinase, galactose-1-P-uridil transferase and UDP-galactose-4-epimerase.[39,40]