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.

Induction of chitinase in response to Aspergillus infection in sorghum (Sorghum bicolor (L) Moench)

“…In carrot under stress, chitinase was induced. 1 The genotypes were further analysed for quantification of chitinase by colorimetry. Chitinase activity was present at all times of fungal infection in both healthy and infected grains.…”

“…1 Chitin is an important component of the cell wall of many fungal pathogens, and chitinase has been shown to inhibit hyphal growth of several fungi in vitro. 2 Thus one of the postulated functions attributed to chitinases in plants is as a defence against fungal infection.…”