Starch amylase inhibitors

The magnitude of inhibition of polygalacturonase was found to be dependent on preincubation of inhibitor with the enzyme. Similar observations have been reported for other enzyme inhibitors (Shivaraj and Pattabiraman, 1980 Sharma and Pattabiraman, 1980 Padmanabhan and Shrasti, 1990). However, preincubation of the inhibitor with substrate did not show any effect on inhibitor activity. In contrast, Shivaraj and Pattabiraman (1980) and Buonocore et al. (1977), have observed inactivation of amylase inhibitor activity on pretreatment with starch. 

Starch blocker A trivial name for the class of drugs (mainly intestinal a-amylase inhibitors) that block dietary conversion of polysaccharides and sucrose to monosaccharides. Such drugs are used in diabetes management, status epilepticus See epilepsy, steady-state In relation to drug metabolism, when the rate of drug intake equals the rate of drug elimination, a steady-state concentration is achieved, stenosis Narrowing or contraction of a duct. 

Unlike the protein protease inhibitors, complexation between the red kidney bean protein a-amylase inhibitor and a-amylase does not appear to Involve binding at the active site of the a-amylase. Evidence for this includes ability of the complex to bind maltose (a competitive inhibitor of a-amylase), starch, Sephadex and to still hydrolyze small substrates. 

Interference of starch metabolism by o-amylase inhibitors. Fed. Am. Soc. Exp. Biol., 33 718 (abstract). 

Puls, W., and Keup, U., 1973, Influence on an a-amylase inhibitor (BAY d 7791) on blood glucose, serum insulin, and NEFA in starch loading tests in rats, dogs, and man. Diabetologia 9 97-101. 

The amylase inhibitor of navy beans is instable in the stomach and becomes active only after preincubation with the enzyme in the absence of starch. As a result, it has no measurable influence on the digestion of starch by human beings. Moreover, the average amounts of inhibitor ingested with the food are small compared to the amylase activity present. 

In addition to the starch properties already described, several starchy foods (for instance, cereals and legumes) have antinutritional factors, such as lectins, tannins, phytates, and enzyme inhibitors (both protease and amylase inhibitors). Amylase inhibitors present in raw pulses may reduce the activity of amylase in the human small intestine. However, most of these factors, especially enzyme inhibitors, are inactivated during food processing and cooking. 

An inhibitor of a-amylase, acarbose, obtained from the red kidney bean, prevents breakdown of starch which, con-... 

For the reasons stated above, deep intrusion of degrading microbes into polysaccharide-plastic films is demonstrably and theoretically improbable. Since starch removal does occur when the films are buried in soil, the primary mechanism must be microbial production of amylase in or near a pore, diffusion of the enzyme into pores and diffusion of soluble digestion products back to the surface where they are metabolized (Figure 3). This mechanism would be the only choice when the pore diameter is too small to admit a microbial cell (i.e., at diameters < 0.5 /im). An alternative mechanism could be diffusion of a water-soluble polysaccharide to the film surface, at which point degradation would occur. None of the materials used in these investigations showed loss of starch even when soaked in water for extended periods with microbial inhibitors present. Therefore, diffusion of amylase to the substrate rather than diffusion of the substrate to the film surface is the more likely mechanism. 

Clearly glycosides of the poiyhydroxylated alkaloids occur widely in nature and it has been possible to produce a- and 3-ghicosides of 1 -deoxynojirimycin by the use of native and immobilised ghicosidases from rice and Rhodotorula lactosa [141], Transglucosylation between 1-deoxynojirimycin and soluble starch has also been posable by using bacterial saccharifying amylase. The a-1,4-glucosyl-deoxynojirimycin produced was shown to be a potent inhibitor of P-amylase [69],... 

Due to the lack of nonreducing glucose residues in the molecule, CDs are not substrates of the exo-type starch-degrading enzymes. In fact, they are potential inhibitors of some amylolytic enzymes such as P-amylase and pullulanase. 

Figure 7 Glycosidase inhibitors that are being tested against diabetes. Acarbose is an inhibitor of amylases and inhibits utilization of starch and glycogen thereby lowering blood glucose levels. Other inhibitors may also have potential use by inhibiting key glycosidases, or other enzymes, that are involved in raising blood glucose levels.

Product Inhibition. In most microbiological and biochemical systems accumulation of end products exercises an inhibitory effect on the rate of the forward reaction. Stimulation by end product is thermodynamically improbable. One of the major products of hydrolysis of cellulose is cellobiose. There is a stimulation by cellobiose of Cx activity of Streptomyces spp. filtrates only when the substrate is solubilized by the introduction of various substituents—e.g., CMC, hydroxycellulose, cellulose acetate, etc. Stimulation is absent when unsubstituted cellulose is used (14). On the other hand, product inhibition is common. Cellobiose inhibits the hydrolysis of cellulose by filtrates of most of the 36 organisms tested. This action of cellobiose is believed to be that of an end product inhibiting an enzymatic hydrolysis in much the same manner that maltose inhibits hydrolysis of starch by a-amylase. The inhibitory effect of products varies with the organism from which the cellulase is derived. Thus, lactose is a very good inhibitor of the enzyme from... 

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