Bovine Serum Chitinase

Abstract

1 A glycol-chitin-splitting enzyme without lysozyme (muramidase) activity has been found in calf serum. The enzyme also degrades colloidal chitin and is thus a true chitinase, 1,4-β-poly-N- acetylglucosaminidase, without exo-β-N-acetylglucosaminidase effect. 2 The enzyme is purified 1000-fold by ion-exchange chromatography and gel filtration. Its optimal activity is between pH 1.5 – 2.0 with glycol chitin and between pH 3 – 6 in a rather broad optimum with colloidal chitin as substrate. The optimal stability of the enzyme is in the pH interval 3.0–6.5 when tested by incubation with glycol chitin at 50 °C for 60 min. The optimal temperature for the degradation of glycol chitin is 40°C when assayed at pH 1.5 and 51°C when assayed at pH 3.5. 3 The enzyme is activated by moderate heating at pH < 6.5. The highest relative activity, 135%, is reached after 45 rnin incubation at 30°C, pH 5 or after 30 rnin at 40°C, pH 2.4. By incubation with small amounts of trypsin at pH 6.5 at 37°C the enzyme was temporarily activated. 4 The isoelectric point, PI 5.3, and the molecular weight, 47000 ± 3000 were determined by respectively isoelectric focusing and gel filtration. 5 The Michaelis-Menten constant, K_m= 0.76 ± 0.05 (S.E.) mg/ml, was measured with glycol chitin as substrate.