Archive | Enzymes

Many enzymes, including lysozyme and ribonuclease, are composed of a single polypeptide chain. Others consist of two or more chains. For example, the en­zyme glycogen phosphorylase consists of two polypep­tide chains; fumarase (a Krebs cycle enzyme) contains four polypeptide chains; and aspartate transcarbamy­lase (involved in the metabolic pathway leading to the synthesis of cytidine triphosphate) consists of 12 polypeptide chains. [...]

Effect of Enzyme on Reaction Rate: Two general mechanisms are involved in enzyme ca­talysis. First, the presence of the enzyme increases the likelihood that the potentially reacting molecular species will encounter each other with the required orientations in space. This occurs because the enzyme has a high affinity for the reactants (more appropri­ately referred to as the substrates) and temporarily [...]

In most instances, the association of the enzyme with the substrate is so fleeting that the complex is ex­tremely difficult to detect. Yet, as early as 1913, L. Michaelis and M. L. Menten postulated the existence of this transient complex. On the basis of their obser­vations with the enzyme invertase, which catalyzes the hydrolysis of sucrose to glucose and fructose, [...]