SUMMARY: Cell-free extracts of eighteen fermentative and nonfermentative Mollicutes were examined for enzyme activities associated with the hexose monophosphate shunt (HMS) and Embden---Meyerhof---Parnas (EMP) pathway. All spp. had glucose-6-phosphate (G6P) dehydrogenase (EC, 6-phosphogluconate (6PG) dehydrogenase (EC and hexokinase (EC activity. Of these three enzyme activities, hexokinase was also detected in sp. Let. 1 but in no other fermentative or nonfermentative spp. The and fermentative spp. possessed all other HMS and EMP activities examined. All spp. possessed a pyrophosphate (PP)-dependent phosphofructokinase (PFK) (EC while fermentative spp. possessed an ATP-dependent PFK (EC Transaldolase (EC activity was detected in some, but not all and fermentative spp. 2-Deoxyribose-5-phosphate aldolase (EC activity was present in all mollicute extracts tested except for and sp. Let. 1. The two nonfermentative spp. lacked all enzyme activities of the HMS pathway except for ribulose-5-phosphate epimerase activity, and of the EMP pathway only phosphoglucose isomerase and the enzymes converting glyceraldehyde 3-phosphate (G3P) to phosphoenolpyruvate (PEP) were detected. We believe that the three major observations of this study are: (1) all spp. lack G6P and 6PG dehydrogenase activities, suggesting a reduction in their NADPH pool, which may relate to the lipid growth requirement of this genus; (2) the fermentative spp. have an ATP-dependent PFK activity, while the fermentative spp. have a PP-dependent PFK activity; and (3) the nonfermentative spp. lack ATP and PP-dependent PFK and fructose-1,6-bisphosphate aldolase activities but, like the fermentative Mollicutes, can convert three-carbon compounds, G3P to PEP through the three-carbon arm of the EMP pathway.


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