Related Experiment Video
Updated: May 11, 2026

Unraveling Entropic Rate Acceleration Induced by Solvent Dynamics in Membrane Enzymes
Published on: January 16, 2016
Effect of length of molecular recognition moiety on enzymatic activity switching
Yuhei Oshiba1, Takanori Tamaki, Hidenori Ohashi
1Chemical Resources Laboratory, Tokyo Institute of Technology, Kanagawa 226-8503, Japan.
Abstract:
We site-specifically conjugated biotin-PEG derivatives with spacer arms of different lengths to mutant P450cam (3mD) and evaluated the activity of and structural changes in the conjugates as a first step toward clarifying the mechanism whereby the activity of the 3mD conjugate is inhibited. 3mD was prepared by site-specific mutation to inhibit its enzymatic activity artificially, after which the derivative compounds were conjugated to the enzyme. 3mD has one cysteine on its surface with a reactive thiol group that can react with compounds near the active site, where a conformational change will be induced after conjugation. The activity of 3mD was retained in the biotin-PEG₂-3mD conjugate, but was dramatically reduced in the biotin-PEG₁₁-3mD conjugate. To investigate the effect of poly(ethylene glycol) (PEG) length on the enzymatic activity after conjugation, PEGs of different lengths, exceeding that in biotin-PEG₁₁, and whose termini were not biotin, were conjugated to 3mD. The activity of 3mD decreased in all these conjugates. This indicates that the activity of 3mD in these conjugates decreased after its conjugation with PEG molecules that exceeded a certain length. The biotin-PEG₂-3mD, which retains enzymatic activity after conjugation, showed avidin responsiveness; the enzymatic activity decreased after avidin binding.
Related Concept Videos
Introduction to Mechanisms of Enzyme Catalysis
Enzymes
Enzyme deficiencies can often translate into life-threatening diseases. For example, a genetic abnormality resulting in the deficiency of the enzyme G6PD...
Induced-fit Model
Enzymes exhibit substrate specificity, meaning that they can only bind to certain substrates. This is mainly determined by the shape and chemical characteristics of...
Enzyme Kinetics
Scientists typically study enzyme kinetics with a fixed amount of enzyme in the controlled environment of a test tube. When more reactant, or substrate, is...
Cooperative Allosteric Transitions
Introduction to Enzyme Kinetics
The experimenter can then plot the initial reaction rate or velocity (Vo) of a given trial against the substrate concentration ([S]) to obtain a graph of the reaction properties. For many enzymatic reactions involving a...

