Abstract:
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 0.1M citrate-phosphate
buffer at pH 6.0 to 7.0 for 30 min. The Km 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 - mercaptoethanol by 1.6 times, while laminarinase
A enzyme was activated by 1.0 mM of CuCl2, FeSO4 and EDTA
with 2.35, 1.38 and 1.57 times respectively. Laminarinase B enzyme was activated
by 1.0 mM Zn SO4 and K2SO4 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.