Crystalline Bacterial Proteinase

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Abstract
It is well known that diisopropyl fluorophosphate (DFP) acts as a specific inhibitor for chymotrypsin, trypsin, and many esterases. Phosphopeptides obtained from their diisopropyl phosphoryl-derivatives are known always to contain a phosphorylated serine residue (1–12), Serine seems to be one of the important amino acids for the proteolytic and esterolytic activity. The histidine residue is also considered to have an important functional significance (13–22), because for example, these enzymes are inactivated as the histidine residue in their proteins is degraded. However, there has been no report that phosphorylated histidine residues have been detected in the hydrolysates of diisopropyl phosphoryl-derivatives of proteinases and esterases. Previously it has been reported that the proteolytic activity of a bacterial proteinase, BPN′, as well as the esterolytic activity were inhibited by DFP. The derivative of BPN′ was isolated in crystalline form (23). Thus, it is natural to investigate the binding site of the phosphorus of DFP and the structure of the peptides adjacent to the active area. In this paper it will be shown that BPN′ reacts stoichiometrically with DFP and the peptides containing phosphorus are composed of Ser*, Gly, Glu or Glu(NH2), and some other amino acids.