Pure Crystalline Rennin

Abstract

NORTHROP¹ has shown that crystallization is a useful procedure in the purification of certain enzymes. Crystalline form, however, is not reliable evidence of purity, as pointed out, for example, by Pirie², but may be considered as confirmatory evidence. For these reasons, in a recent attempt in this laboratory to obtain pure rennin, conditions favouring crystallization have been chosen. A preparation consisting largely of flat crystalline plates but containing a small proportion of spheroids has been obtained. From the accompanying photomicrographs it can be seen that although the outline of the plates is irregular, it tends to be triangular or rectangular, that the bounding surfaces are plane, and that the small surfaces forming the 'edges' of the plates are at right angles to the main surfaces. The latter conclusion arises from the rectangular appearance of the plates when seen 'on edge'.