ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...
ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ... ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...
Optimum pH for amylase inlnbitor activity in Colocasia esculenta is shown in Figure Bl-3.6. A two-peakpattemwas found, which showed an optimum at pH 4.0 and 6.0. 35 3D 2S 120 .. ,. ,. ,. • • • 2 4 • • ,. 12 Figure BI-3.6: Effect ofpH on the stability ofAmadumbe a-amylase inhibitor pH The enzyme solutions at varions pH values were incubated at 25° C for 10 minutes and residual activity was measured as descnbed in Appendix B. 136
Bl.4.1 B1.4.2 Introduction CHAPTER B1-4 DISCUSSION In this chapter, the results ofthe isolation, partial purification and characterization ofthe two a-amylase inhtbitors from Amadumbe are discussed. Isolation ofa-amylase inhibitor A 3.89- and 4.42-fold purification ofAI-AI and AI-B2 respectively was obtained. The proteins had specific activity of I 1.29 and 12.83 respectively. The purified a-amylase inhtbitors (AI-AI and AI-B2) from Colocasia esculenta showed a molecular weight ofapproximately 17 kDa and 19 kDa respectively. The little available information on a-amylase inhibitors present in Colocasia antiquorum (Sharma and Pattabiraman, 1980), taro (Seltzer and Strumeyer, 1990) and sweet potato (Rekha et al., 2004) seemed to indicate that most tubers had two proteins that showed inhibiting activity. The molecular weight ofthese proteins ranged between I I and 25 kDa. B1.4.3 Kinetic studies B1.4.3.1 Action ofinhibitors on different a-amylases a-Amylase inhibitors show strict target enzyme specificity and recognize ouly one out of several closely related isoenzymes or enzymes from different species (Weselake et aI., 1983; Franco et aI., 2000). Payan (2004) observed that amylase-inhtbitor complexes have general features ofinhtbition on different amylases: (i) the inhibitor inhibits primarily via interactions with the enzyme substrate active site (ii) side-chains originating from the 137
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Optimum pH for amylase inlnbitor activity in Colocasia esculenta is shown in Figure<br />
Bl-3.6. A two-peakpattemwas found, which showed an optimum at pH 4.0 and 6.0.<br />
35<br />
3D<br />
2S<br />
120 .. ,.<br />
,.<br />
,.<br />
•<br />
• • 2 4 • • ,. 12<br />
Figure BI-3.6: Effect ofpH on the stability ofAmadumbe a-amylase inhibitor<br />
pH<br />
The enzyme solutions at varions pH values were incubated at 25° C for 10 minutes and<br />
residual activity was measured as descnbed in Appendix B.<br />
136
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