Crystallization of salt-free chymotrypsinogen and chymotrypsin from solution in dilute ethyl alcohol

Chymotrypsinogen and chymotrypsin crystallize readily from dilute solutions of ethyl alcohol in the absence of salts. The crystals formed in the presence of alcohol differ in appearance from those formed in the presence of ammonium sulfate. Chymotrypsinogen yields well formed polyhedrons instead of fine needles usually produced in ammonium sulfate solution. Chymotrypsin yields fine needles in the presence of alcohol and rhombohedrons in the presence of ammonium sulfate. The enzymatic properties of the crystals formed in the presence of alcohol are identical with those of the crystals isolated in the presence of ammonium sulfate.     

Comparisons of diisopropylfluorophosphate derivatives of chymotrypsin and chymotrypsinogen by phosphorus-31 nuclear magnetic resonance

The nature of the differences in the active sites of α-chymotrypsin and chymotrypsinogen has been investigated by phosphorus-31 NMR studies of their diisopropylfluorophosphate derivatives. The phosphorus-31 resonance of the modified zymogen occurs 2 ppm upfield from that for the enzyme. An even greater separation is seen between diisopropylphosphoryl-neo-chymotrypsinogen and -α-chymotrypsin. A plausible interpretation of the chemical shift differences is based on the known structures for α-chymotrypsin, chymotrypsinogen and diisopropylphosphoryl-trypsin.     

High resolution nuclear magnetic resonance study of the histidine--aspartate hydrogen bond in chymotrypsin and chymotrypsinogen

A high resolution proton nuclear magnetic resonance study of chymotrypsin A_δ and Chymotrypsinogen A in water has shown a single resonance at very low magnetic fields (− 18 to − 15 p.p.m. relative to dimethyl-silapentane-sulfonate). From its pH dependence (pK = 7·2) and response to chemical modification the resonance has been assigned to the hydrogen-bonded proton between His-57 and Asp-102.