Enzymes catalyzing the deamidation of seed storage proteins were found in germinating seeds of kidney beans (Phaseolus vulgaris L. cv. Moldavian) and squash (Cucurbita pepo L. cv. Mozoleevskaya). They were partially purified and characterized. The properties of these enzymes closely resemble those of the protein deamidase in germinating wheat grains. The detection of similar protein deamidases in germinating seeds of plants belonging to phytogenetically unrelated species indicates that protein deamidases are of considerable physiological significance.