Enzymes of starch degradation and synthesis.

Thiol groups of biological importance.

Publisher Summary This chapter outlines the recent developments in the amylase field, with a discussion of the emerging fields of biosynthesis and the control of amylase action The International Commission on Enzymes has recommended a standard method for expressing enzymic activity as the number of micromoles of substrate transformed under defined conditions by an enzyme The production of new reducing ends is most frequently followed by the 3,5-dinitrosalicylate, alkaline ferricyanide, or alkaline copper methods, or by oxidation of glucose with glucose oxidase The simplest and the least desirable alkaline oxidation method involves reduction of 3,5-dinitrosalicylate With this method, reducing equivalents for equimolar amounts of substrates increases significantly with increasing chain length Measurements are subject to interference by Ca 2+ used to stabilize amylases and are relatively insensitive It has the advantage of highest sensitivity and precision, low and stable background, and is relatively insensitive to a wide range of contaminating substances Ironically, its greatest disadvantage is its high sensitivity leading to high substrate backgrounds This problem can be circumvented by borohydride reduction of the substrate

6 Plant and Animal Amylases

A crystalline beta-amylase from sweet potatoes.

Publisher Summary This chapter considers those chemical reactions that can be used to modify native proteins under such mild conditions that little or no denaturation may be expected. It is of considerable importance that no denaturation takes place, for if denaturation assumes appreciable proportions the system is very complicated and no reliable interpretation can be made of the results. Very few workers have established the fact that a chemical reaction has been carried through involving specific groups of a protein without denaturing the protein in the process. A few instances have been discussed in the present chapter in which denaturation undoubtedly accompanied the chemical reaction under examination. A correlation of the number of specific protein groups modified with the number of reagent residues introduced into the protein is another desirable feature of any study of the type covered by this chapter. In the case of oxidation or reduction reactions in which no reagent residues are attached to the protein the stoichiometry of the reaction provides equivalent information.

C. Edwin Weill

Papers

A Study of the Essential Groups of β-Amylase.1

A Study of the Essential Groups of β-Amylase.1II. Sulfhydryl Groups

Further Studies of the Essential Groups of Pancreatic Amylase