Amylose binding

Thus, randomly coiled amylose binds I3 ions, and this interaction is responsible for the helical structure of amylose. Helical amylose arrests iodine and further I3 anions, a process which is cooperative. If the filling of one helix commences, then the filling of another helix proceeds once the former helix is full. The longest available helix has priority in the uptake... 

The iodine affinity is due to the formation of colored complexes with amylose. The color of this complex depends on both the concentration of the iodine in the solution and the kind of starch. Amylose binds 20% (v/v) of iodine, to develop a blue color, whereas amylopectin binds only O.S to 1% (v/v) of iodine to give a red-violet eolor. Starch which does not contain any amylose gives a red color with iodine. Thus, evaluation of the degree of dextrinization based on the observations of Komm and Martin needs standardization of the method and approach, because ofthe variability in the origin of the starch. Table XVI shows that methods in use to date are not equivalent to one another. The color-development characteristics are again dependent on the origin of the starch. ... 

Epichlorohydrin-cross-linked cyclohexa- and cyclohepta-amylose gels have been used for the chromatographic resolution of racemic mandelic acid and its derivatives. Modified cyclohepta-amylose bound the L-(- -)-isomers preferentially, and resolved D,L-methyl mandelate to give the D-(—)-isomer of 100% optical purity in the first fraction. Cross-linked cyclohexa-amylose bound D-(—)-isomers more strongly than L-(-t-)-isomers, resolving D,L-methyl mandelate to a smaller extent than cross-linked cyclohepta-amylose. Binding was studied quantitatively by the equilibrium method. 

FIGURE 6.16 AFM images of glucoamylase-amylose complexes and binding models. 

A) Circular amylose-GA-1 complex and (B) corresponding binding model the balls represent starch-binding domain (SBD) and the lines represent amylose chains (C) linear amylose-mutant GA-1 complex and (D) corresponding binding model. Image size ... 

Morris, V. J., Gunning, A. P., Faulds, C. B., Williamson, G., and Svensson, B. (2005). AFM images of complexes between amylose and Aspergillus niger glucoamylase mutants, native, and mutant starch binding domains A model for the action of glucoamylase. Starch-Starke 57,1-7. 

Hui et al. 177) have investigated the inclusion compounds between carboxymethyl-amylose and the two aromatic keto-acid salts (30) and (31). The binding constants... 

Values of /c2 and Kd for the reactions of the cycloamyloses with a variety of phenyl acetates are presented in Table IV. The rate constants are normalized in the fourth column of this table to show the maximum accelerations imposed by the cycloamyloses. These accelerations vary from 10% for p-f-butylphenyl acetate to 260-fold for m-f-butylphenyl acetate, again showing the clear specificity of the cycloamyloses for meta-substituted esters. Moreover, these data reveal that the rate accelerations and consequent specificity are unrelated to the strength of binding. For example, although p-nitrophenyl acetate forms a more stable complex with cyclohexa-amylose than does m-nitrophenyl acetate, the maximal rate acceleration, h/kan, is much greater for the meta isomer. 

The anions of CDs may also function as simple basic catalysts towards acidic substrates included in their cavities. Such was observed by Daffe and Fastrez (1983) who studied the deprotonation and hydrolysis of oxazolones in basic media containing CDs. Also, in a paper dealing mainly with catalysis by amylose, it was noted that CDs catalyse the deprotonation of long chain /3-keto esters in basic aqueous DMSO (Cheng et al., 1985) no saturation kinetics were found for CDs, indicating weak substrate binding under the conditions used. 

The dependence of the mobilities of amylopectin and amylose on iodine concentration in the background electrolyte and applied temperature was studied by Brewster et al. (111). The method was used for the separation and identification of different plant starches, but no binding constants were calculated. 

Akiyoshi K, Maruichi N, Kohara M, Kitamura S. Amphiphilic block copol3mier with a molecular recognition site induction of a novel binding characteristic of amylose by self-assembly of polyfethylene oxidej-fetock-amylose in chloroform. Biomacromolecules 2002 3 280-283. 

Maltose binding protein crosslinked amylose Yes Bedouelle and Duplay, 1988... 

An interesting observation is that an enzyme may exhibit different pH activity profiles for various neutral substrates. The explanation of this is that the enzyme binds or transforms such various substrates differently. For example. Taka amylase has different pH optima for long chain amyloses and for low molecular mass substrates. Some specific chemical modifications of the side chains of the enzyme may also alter the pH activity profiles. Kobayashi, Miura and Ichisima (1992) modified the lysine amino groups using bifimctional reagent o-phtalaldehyde, and observed a pronounced shift in the pH-dependence of ohgomaltoside hydrolysis. 

To determine the amylose content of starch, the iodine reaction has been most commonly used because amylose and amylopectin have different abilities to bind iodine. The methods such as blue value (absorbance at 680 nm for starch-iodine complex using amylose and amylopectin standards), and potentiometric and amperometric titration have been used for more than 50 years. These procedures are based on the capacity of amylose to form helical inclusion complexes with iodine, which display a blue color characterized by a maximum absorption wavelength (kmax) above 620 nm. During the titration of starch with iodine solution, the amount (mg) of iodine bound to 100 mg of starch is determined. The value is defined as iodine-binding capacity or iodine affinity (lA). The amylose content is based on the iodine affinity of starch vs. purified linear fraction from the standard 100 mg pure linear amylose fraction has an iodine affinity of 19.5-21.0mg depending on amylose source. Amylopectin binds 0-1.2mg iodine per 100mg (Banks and Greenwood, 1975). The amylose content determined by potentiometric titration is considered an absolute amylose content if the sample is defatted before analysis. 

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