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. 2022 Apr 12;61(24):e202117724. doi: 10.1002/anie.202117724

Figure 1.

Figure 1

PL probe library and activation by pyridoxal kinase. A) Activation of PL occurs by phosphorylation with pyridoxal kinase (PLK) to form PLP, which can bind PLP‐DEs via an internal aldimine to an active site lysine residue. Reaction with substrate amines leads to the formation of external aldimines, which can undergo various reactions via quinonoid structures. B) Structures of first [13] and second generation PL probes applied in this study. Type A probes are derivatised at the C2′, type B probes at the C6 and one type C probe is modified at the C3′. C) Activation of PL probes by pyridoxal kinases (E. coli pdxK or S. aureus SaPLK) were monitored by measuring UV/Vis absorbance over time (every 40 min, 20 cycles, n=3, mean±SEM). Phosphorylated species absorb at around 395 nm, unphosphorylated around 320 nm. Phosphorylation efficiency is depicted by comparing the absorbance [a.u.] from phosphorylated species (PLX, X=1–13) at the beginning (PLXPinit ) and at the end (PLXPend ). For PL6 SaPLK phosphorylation, the difference of initial and final absorbance at wavelengths of the unphosphorylated compound is depicted. For PL13, phosphorylated compound absorbed at 320 nm. Raw data of all compounds are shown in Figure SI1, 2.