Plant α‐amylase inhibitors and their interaction with insect α‐amylases

Abstract

Insect pests and pathogens (fungi, bacteria and viruses) are responsible for severe crop losses. Insects feed directly on the plant tissues, while the pathogens lead to damage or death of the plant. Plants have evolved a certain degree of resistance through the production of defence compounds, which may be aproteic, e.g. antibiotics, alkaloids, terpenes, cyanogenic glucosides or proteic, e.g. chitinases, b-1,3-glucanases, lectins, arcelins, vicilins, systemins and enzyme inhibitors. The enzyme inhibitors impede digestion through their action on insect gut digestive a-amylases and proteinases, which play a key role in the digestion of plant starch and proteins. The natural defences of crop plants may be improved through the use of transgenic technology. Current research in the area focuses particularly on weevils as these are highly dependent on starch for their energy supply. Six dierent a-amylase inhibitor classes, lectin-like, knottin-like, cereal-type, Kunitz-like, c-purothionin-like and thaumatin-like could be used in pest control. These classes of inhibitors show remarkable structural variety leading to dierent modes of inhibition and dierent speci®city pro®les against diverse a-amylases. Speci®city of inhibition is an important issue as the introduced inhibitor must not adversely aect the plant's own a-amylases, nor the nutritional value of the crop. Of particular interest are some bifunctional inhibitors with additional favourable properties, such as proteinase inhibitory activity or chitinase activity. The area has bene®ted from the recent determination of many structures of a-amylases, inhibitors and complexes. These structures highlight the remarkable variety in structural modes of a-amylase inhibition. The continuing discovery of new classes of a-amylase inhibitor ensures that exciting discoveries remain to be made. In this review, we summarize existing knowledge of insect a-amylases, plant a-amylase inhibitors and their interaction. Positive results recently obtained for transgenic plants and future prospects in the area are reviewed.Keywords: a-amylase inhibitors; knottin-like; lectin-like; thaumatin-like; Kunitz; cereal-type; bean weevils; bifunctional inhibitors.Insect pests and pathogens such as fungi, bacteria and viruses are together, responsible for severe crop losses. Worldwide, losses in agricultural production due to pest attack are around 37%, with small-scale farmers hardest hit [1]. Starchy leguminous seeds are an important staple food and a source of dietary protein in many countries. These seeds are rich in protein, carbohydrate and lipid and therefore suffer extensive predation by bruchids (weevils) and other pests. The larvae of the weevil burrow into the seedpods and seeds and the insects usually continue to multiply during seed storage. The damage causes extensive losses, especially if the seeds are stored for long periods.In general, plants contain a certain degree of resistance against insect predation, which is re¯ected in the limited number of insects capable of feeding on a gi...

An investigation on acarbose inhibition and the number of active sites in an amylopullulanase (L14-APU) from an Iranian Bacillus sp.

“…b Expressed as % of control. (Desseaux et al 2002;Franco et al 2002). In the case of barley α-amylase, the acarbose is a non-competitive inhibitor with inhibition constant for maltoheptaose in the µM range (Oudjeriouat et al 2003).…”

“…Kinetic analysis of this inhibition revealed that it was a competitive inhibitor of pullulytic and amylolytic activities of the enzyme. The class of non-proteinaceous α-amylase inhibitors, such as acarbose, isoacarbose, acarviosin-glucose and the CDs could bind to α-amylase catalytic site and inhibit the enzyme Franco et al 2002). Up to now the effect of acarbose on different amylolytic enzymes such as pig pancreatic α-amylase (PPA) (Koukiekolo et al 2001;Desseaux et al 2002), human pancreatic α-amylase (HPA) (Nahoum et al 2000), barley α-amylase isozymes (Oudjeriouat et al 2003), cyclodextrin glycosyltransferase (Leemhuis et al 2003), glucoamylase (Gasperik et al 2005), 4-α-glucanotransferase (Tang et al 2006), and catalytic domain of the pullulanase type II from an archaebacterium Thermococcus hydrothermalis (Chang-Pi-Hin et al 2002) has been studied.…”

“…Acarbose is a pseudosaccharide inhibitor of α-amylases that acts like a transition-state analogue (Kagawa et al 2002;Oudjeriouat et al 2003) and binds to the active site. The CDs inhibit some α-amylases and the mechanism of their inhibition is pH-, temperature-and substrate-dependent (Franco et al 2002). Here we describe the influence of these α-amylase inhibitors and their inhibitory effects toward the L 14 -APU.…”

A Review: Biological and Technological Functions of Barley Seed Pathogenesis-Related Proteins (PRs)

“…A database for plant PIs is accessible at http://bighost.area.ba.cnr.it/ PLANT-PIs 261 . Several reviews on mode of action, structure and function of protease and/or α-amylase inhibitors have recently been published 95,116,117,162,178,224,254,326 .…”

Importance of amylases for physiological quality in maize seeds

“…It constitutes a family of endoamylases that catalyze the hydrolysis of glycosidic linkages between α-1.4 starch, glycogen, and other carbohydrates (FRANCO et al, 2002). β-amylase is an α-1.4-D-glucan maltohydrolase (EC 3.2.1.2.)…”