Chitinase, laminarinase A and laminarinase B were extracted and purified from Egyptian sugar beet (Beta vulgaris) leaves. Chitinase showed higher heat stability than laminarinase A and laminarinase B when heated at 50°C for 60 min. Chitinase activity was quite stable in water than in buffer, while laminarinase A and laminarinase B activities increased when incubated with 0.1 M citrate-phosphate buffer at pH 6.0 to 7.0 for 30 min. The K m values of chitinase, laminarinase A and laminarinase B were 0.2, 0.27 and 0.074% at pH's 4.5, 4.5 and 6.5 using colloidal chitin, laminarin A and laminarin B as substrates respectively. Chitinase enzyme was activated by 0.75 mM a-mercaptoethanol by 1.6 times, while laminarinase A enzyme was activated by 1.0 mM of CuC1 2 , FeSO 4 and EDTA with 2.35, 1.38 and 1.57 times respectively. Laminarinase B enzyme was activated by 1.0 mM Zn SO 4 and K 2 SO 4 with 1.3 and 1.18 times respectively. Chitinase, laminarinase A and laminarinase B enzymes have an endo-splitting type of activity. They were able to inhibit the growth and to lyse cell walls of Aspergillus oryza and A. flavus either alone or in combination through the degradation of chitin and laminarin.

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