The purification and characterization of a Trichoderma harzianum exochitinase

A chitinolytic enzyme was purified from the culture filtrate of T. harzianum (T198) by precipitation with ammonium sulphate followed by affinity binding to swollen chitin and release with 10% (v/v) acetic acid. The molecular weight of the enzyme was calculated to be 28 and 27.5 kD by gel filtration chromatography and SDS-PAGE, respectively. The isoelectric point of the enzyme was 7.4. The pH optimum for activity was 3.5 and maximum activity was obtained at 50 degrees C. The enzyme displayed activity on a wide array of chitin substrates of more than two N-acetylglucosamine units in length. HPLC analysis of hydrolysis products demonstrated that the enzyme was an exochitinase releasing N-acetylglucosamine only.