Amylose hydrolysis

Figure 5. Lineweaver-Burk plots of amylose hydrolysis rates in the presence of the random copolymer at various temperatures. Temp (A) 85°, (A) 80°, (%) 75°, and (O) 70°C. [Catalyst] = 2.00 X W3N.

The inhibition effect of poly (vinyl alcohol) on the amylose hydrolysis was investigated. Figure 7 shows Lineweaver-Burk plots of the amylose hydrolysis rates catalyzed by the random copolymer in the presence of poly (vinyl alcohol). The reaction rate is found to decrease with increasing the concentration of poly (vinyl alcohol), and all of the straight lines obtained in the plots cross with each other at a point on the ordinate. This is a feature of the competitive inhibition in the enzymatic reactions. In the present reaction system, however, it is inferred to suggest that the copolymer and poly (vinyl alcohol) molecules competitively absorb the substrate molecules. The elementary reaction can be described in the most simplified form as in Equation 3 where Z, SI, and Kj[ are inhibitor, nonproductive complex, and inhibitor constant, respectively. Then the reaction rate is expressed with Equation 4. 

Enzymes involved in the cleavage of carbohydrates can also function by the above mechanism. Figure 2.18 shows that amylose hydrolysis by p-amylase occurs with the help of four functional groups in the active site. The enzyme-substrate complex is subjected to a nucleophilic attack... 

Fig. 2.35. Fungal a-amylase. Amylose hydrolysis versus temperature. Arrhenius diagram for assessing the activation energy of enzyme catalysis and enzyme inactivation V = total reaction rate...

Amylase occurs in many plants, such as barley, wheat, rye, soy beans, and potatoes, where it is generally accompanied by some a-amylase. [ -Amylase initiates hydrolysis at the nonreducing end of an amylose or amylopectin chain, and removes maltose units successively until the reducing end of the molecule is encountered in amylose or a branch is met in amylopectin. ( -Amylase is used commercially in the preparation of maltose symps. After P-amylase hydrolysis of amylopectin there remains a P-amylase limit dextrin. ( -Amylase has been used as a probe of the fine stmcture of amylopectin (43-46). 

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

An early report from Shukla et al.129 showed efficient hydrolysis and isomerization reactions of disaccharides, including cellobiose, maltose, and lactose, over zeolites type A, X, and Y. Abbadi et al.130 studied the hydrolysis of maltose, amylose, and starch over the zeolitic materials H-mordenite, H-beta, and mesoporous MCM-41. The effect of temperature and pressure, as well as that of the Si/Al ratio of H-mordenite and H-beta zeolites, on their catalytic activity was investigated for the... 

The rate of hydrolysis of amylose in 7.7 N hydrochloric acid has been measured by Swanson and Cori,146 who, from comparison of this result with that for amylopectin, concluded that the 4 — 1-a-D bonds are less stable than the 6 — 1-a-D type. 

Especially in the US and European markets, amylases have been added to detergents along with proteases since 1973 to capitalize on the activity of the amylases toward starch-containing soils. From different amylases available, only a-amylases are used for detergents. They are able to catalyze the hydrolysis of the amylose and amylopectin fractions of starch, i.e., cleavage of the a-l,4-glycosidic bonds of the starch chain [15]. This facilitates the removal of starch-based stains by the detergent. 

Products.—Considerable information concerning the mechanism of the enzymic hydrolysis of starch has been obtained from investigations of the action of purified maltase-free pancreatic amylase on a number of different substrates. The substrates studied were ordinary unfractionated but exhaustively defatted10 potato and com starches a branched chain substrate, waxy maize starch and amylose, the linear component of corn starch.41 69 eo f4 These investigations included comparisons not only of the rates of the hydrolysis of the different substrates but also of the products formed from them. 

A Comparison of the Hydrolysis of Potato Starch and of Com Amylose by Purified Maltase-free Pancreatic Amylase (Data of Alfin and CaldwellM)... 

The hydrolysis of amylose by malt alpha amylase has been investi-... 

Tables XI and XII summarize data obtained by Myrback86 for the hydrolysis of amylose by purified maltase-free malted barley alpha amylase. The hydrolysis curve with this linear substrate is much the same as those obtained with unfractionated starches, and also is similar to the curves representing the hydrolysis of amylose by pancreatic amylase.41 The flattening of the hydrolysis curves during the later stages (86) K. H. Meyer and P. Bernfeld, Helv. Chim. Acta, 24, 359E (1941).

Both maltose and glucose were present in the reaction mixtures with amylose,85 (Table XI). Therefore, glucose is liberated in addition to maltose from this straight-chain substrate as well as from unfractionated starch by maltase-free malted barley alpha amylase (Table IX). 4 It appears from the results reported by Myrback (Table XI) 5 that amylose can be hydrolyzed completely to fermentable sugar by malted barley alpha amylase but only after a prolonged period of hydrolysis (32 days). A more recent report by Myrb ck87 confirms and extends this con-(87) K. Myrbftck, Arch. Biochem., 14, S3 (1947). 

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. 

Exhaustive studies on well-defined systems are rather scarce (4) nevertheless 3 systems thoroughly analyzed by independant research groups are of outstanding interest a) the quaternization of polyvinylpyridines by alkyl halogenides (20-25) b) the chlorination of polyethylene (13,26-28) c) the basic or acid hydrolysis of PMMA (29-31). On the other hand, neighbouring groups effects have been quantitatively taken into account for the kinetic analysis of periodate oxidation of amylose (32,33). 

Hammett substituent constant, effect of cyclo-amyloses on, in hydrolysis of phenyl esters, 23 222... 

---