Enzymes and Fermentation in Yeast Cells 279 



phosphate concentration. Hence, only an initial surplus 

 production of fructose diphosphate due to the phosphorylation 

 of fructose-6-phosphate or an initially too low dehydrogena- 

 tion of phosphoglyceraldehyde phosphate by triose phosphate 

 dehydrogenase comes into question for the occurrence of a 

 maximum of the concentration of fructose diphosphate. 



16.0 ^ 



e.o S- 



10 20 30 40 50 60 70 60 90 100 ^ sec 



Fig. 2. Changes in metabolite concentrations after the addition of 



glucose to starved yeast cells under anaerobic conditions (From 



Holzer and Freytag-Hilf, 1959. Reproduced by permission of the 



Editors, Biochem. Z.). 



These are the two enzymes, between the activities of which the 

 substances fructose diphosphate, dihydroxyacetone phosphate 

 and phosphoglyceraldehyde are found. 



A reductive alteration of dihydroxyacetone phosphate to a-gly- 

 cerophosphate need not be taken into consideration in yeast cells, 

 since a specific enzyme for this reaction does not exist. This reaction 

 is unspecifically catalysed by the enzyme alcohol dehydrogenase and 

 takes place only if there exist unphysiologically high concentrations 

 of reduced diphosphopyridine nucleotide (DPNH) and dihydroxy- 

 acetone phosphate (e.g. in the so-called sulphite fermentation). 



