ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

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
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