Chitinase profiles in mature carrot (Daucus carota) roots and purification and characterization of a novel isoform

Abstract

The profile of chaitinases (EC 3.2.1.14) in mature carrot (Daucus carota L. cv. Eagle) roots was studied. Multiple chitinase bands (8–10) were observed in native and sodium dodecylsulfate‐denaturing polyacrylamide gels. The molecular masses of these chitinases were estimated to be from 20 000 to 40 000. One major chitinase was purified and found to be an acidic protein with pI at 4.3 and a molecular mass of 39 500. The optimum pH for enzymatic activity was around 5 and the optimum temperature was 25°C. The enzyme was stable at pHs below 8 and temperatures below 60°C. The protein did not have a chitin‐binding domain, but showed some similarity to the amino acid composition of tobacco class I chitinase. The N‐terminal amino acid sequence did not resemble any of the described classes of chitimases. This chitinase did not possess lysozyme activity and showed antifungal activity when tested against Trichoderma sp.