ases by specific proteins present in plants as well as animals. Other enzymes besides proteinases can be inhibited by proteins. A protein inhibitor of potato invertase was detected when an inhibitor-containing enzyme extract exhibited a nonlinear increase in activity with a linear increase in protein concentration. It was proposed that inhibition occurs by irreversible binding of the inhibitor to the enzyme; inhibition was noncompetitive. A metabolic role for the inhibitor was suggested when large amounts of the inhibitor and low invertase activity were found in tubers stored at 18 C and the reverse at 4 C (3-5).

A bound invertase and two soluble invertases are found in the developing endosperm of maize (Zea mays L.). The two soluble invertases can be separated on diethylaminoethyl-cellulose and Sephadex columns and distinguished by their kinetic constants. One soluble invertase, invertase I, is present from the 10-to 28-day stages of endosperm development with maximal activity per normal endosperm at the 12-day stage. In two endosperm mutant lines, shrunken-I and shrunken-2, there is a second increase in invertase I activity later in development which could be a secondary effect caused by the abnormal metabolism in these lines. Another soluble invertase, invertase II, is present in the embryo upon germination and is also found in the very young developing endosperm (6-day stage).The third form of invertase, bound invertase, is present in the endosperm by the 6-day stage, and its activity remains approximately constant during development.

In a recent paper Eberhart and Beck (4) suggested that the aryl-,B-glucosidase of Neurospora conidia is a mural enzyme. Similarly, Nevins (11) reported that ,-glucosidase is strongly associated with cell walls during extraction of bean hypocotyls at pH 4.6 and suggested that this enzyme is wall-bound in situ, and Keegstra and Albersheim (9) ,B-Glucosidase was extracted from the hypocotyls of beans (Phaseolus vulgaris L. var. Red Kidney) which had been allowed to germinate for 5 days at room temperature between moist paper towels. The bean seeds were obtained from a local market. Extraction and centrifugation procedures were similar to those used for sweetclover preparations.The cellular debris used in some preincubation experiments was prepared from sweetclover leaves which had been frozen in liquid nitrogen, pulverized in a mortar, lyophilized, and stored in a freezer. A 1-g portion of this material was suspended in 20 ml of 50 mm borate buffer, pH 8.5, and the suspension was centrifuged at 17,000g for 10 min. The pellet was subjected to three additional washings with buffer, one with water, and a final washing with acetone. The washed pellet was air-dried.Preincubation mixtures consisted of 1.0 ml of deionized enzyme preparation; 0.5 ml of water, 81 mm acetate buffer, pH 5.0, or 81 mm borate buffer, pH 8.5; and, in some instances, 5 mg of cellular debris. Mixtures were allowed to stand for 5 min at room temperature and were then centrifuged. Supernatant fractions from this centrifugation were assayed for ,Bglucosidase activity. Pellets were resuspended in 1.5 ml of 50 mM borate buffer, pH 8.5, and recentrifuged. Assay of BO-glucosidase activity in the supernatant fractions from this centrifugation provided a measure of the activity which was associated with the pellet at the end of the preincubation treatment.