Comparative studies on lens neutral endopeptidase and pituitary neutral proteinase: two closely similar enzymes.

A neutral endopeptidase (EC 3.4.24.5) previously thought to be unique to the eye lens has been found to be closely similar if not identical in native molecular size, component polypeptides and antigenic structure to a neutral proteinase from pituitary. Here we investigated some subtle differences in properties of the two enzymes, such as the effects of temperature, divalent cations and SDS on their activities with respect to different substrates. We conclude that the pituitary enzyme may have a relatively more compact structure requiring relaxation by low SDS concentration or higher temperature for maximum activity.