Cleavage of Aliphatic Α-Hydroxy Ketones by Evolved Transketolase from Geobacillus Stearothermophilus

The reaction catalyzed by ubiquitous thiamine pyrophosphate-dependent transketolase engaged in cells in the pentose phosphate pathway can be applied in vitro to the cleavage of aliphatic alpha-hydroxy ketones with thermostable transketolase variants from Geobacillus stearothermophilus obtained through rational design. The simple variant F435I gave the best activity toward (3S)-1,3-dihydroxyhexan-2-one 3, leading to the corresponding product with 92% yield after only 2 h of reaction time. Three triple variants H102L/H474 (S, G, or A)/F118I were found to cleave (+/-)-4-hydroxyhexan-3-one 6, giving the corresponding product with 90, 82, and 79% yield, respectively, after 24 h, whereas wild-type transketolase was almost ineffective. This biocatalytic strategy offers a promising one-step alternative to other multienzyme or chemical ways for the cleavage of aliphatic alpha-hydroxy ketones.