Photoinactivation of aldolases by pyridoxal phosphate and its analogues

The Effect of Visible Light on the Catalytic Activity of PLP-Dependent Enzymes

Pyridoxal 5'-phosphate (PLP)-dependent enzymes are a versatile class of biocatalysts and feature a variety of industrial applications. However, PLP is light sensitive and can cause inactivation of enzymes in certain light conditions. As most of the PLP-dependent enzymes are usually not handled in dark conditions, we evaluated the effect of visible light on the activity of PLP-dependent enzymes during production as well as transformation. We tested four amine transaminases, from Chromobacterium violaceum, Bacillus megaterium, Vibrio fluvialis and a variant from Arthrobacter species as well as two lysine decarboxylases, from Selenomonas ruminantium and the LDCc from Escherichia coli. It appeared that five of these six enzymes suffered from a significant decrease in activity by up to 90 % when handled in laboratory light conditions. Surprisingly, only the amine transaminase variant from Arthrobacter species appeared to be unaffected by light exposure and even showed an activation to 150 % relative activity over the course of 6 h regardless of the light conditions.