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Abstract
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Chitinases have the ability of chitin digestion that constitutes a main compound of the cell wall in many of
the phytopathogens such as fungi. In the following investigation, a novel chitinase with antifungal activity
was characterized from a native Serratia marcescens B4A. Partially purified enzyme had an apparent
molecular mass of 54 kDa. It indicated an optimum activity in pH 5 at 45?C. Enzyme was stable in 55C for
20 min and at a pH range of 3-9 for 90 min at 25C. When the temperature was raised to 60°C, it might
affect the structure of enzymes lead to reduction of chitinase activity. Moreover, the Km and Vmax values for
chitin were 8.3 mg/ml and 2.4 mmol/min, respectively. Additionally, the effect of some cations and chemical
compounds were found to stimulate the chitinase activity. In addition, Iodoacetamide and Idoacetic acid did
not inhibit enzyme activity, indicating that cysteine residues are not part of the catalytic site of chitinase.
Finally, chitinase activity was further monitored by scanning electronic microscopy data in which
progressive changes in chitin porosity appeared upon treatment with chitinase. This enzyme exhibited
antifungal activity against Rhizoctonia solani, Bipolaris sp, Alternaria raphani, Alternaria brassicicola,
revealing a potential application for the industry with potentially exploitable significance. Fungal chitin
shows some special features, in particular with respect to chemical structure. Difference in chitinolytic
ability must result from the subsite structure in the enzyme binding cleft. This implies that why the enzyme
didn't have significant antifungal activity against other Fungi.
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