Snapshots of PLP‐substrate and PLP‐product external aldimines as intermediates in two types of cysteine desulfurase enzymes

Cysteine desulfurase enzymes catalyze sulfur mobilization from l‐ cysteine to sulfur‐containing biomolecules such as iron‐sulfur (Fe‐S) clusters and thio‐tRNAs. The enzymes utilize the cofactor pyridoxal‐5'‐phosphate (PLP), which forms the external substrate‐ and product‐aldimines and ketimines during catalysis and are grouped into two types (I and II) based on their different catalytic loops. To clarify the structure‐based catalytic mechanisms...