Ketosteroid Isomerase

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Contents 1 Introduction 2 Structure 3 Enzyme Mechanism 4 Related Proteins 5 Available Structures

Introduction

spinqualitylabelsall models Ketosteroid Isomerase (KSI; PDB 1ISK) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Ketosteroid isomerase (KSI, EC#5.3.3.1) is an enzyme that catalyzes the isomerization of 3-oxo-Δ⁵ ketosteroids to their hormonally active Δ⁴-conjugated isomers.

This reaction is essential in the biosynthesis of steroids in mammals where KSI is a membrane-bound complex. In bacteria, however, KSI exists as a soluble protein is involves in catabolism of steroids. It is one of the most proficient known enzymes with an essentially diffusion limited rate of catalysis. An NMR solution phase structure of KSI

Structure

Ketosteroid isomerase exits as a 28 kDa homodimeric protein.

Enzyme Mechanism

Related Proteins

Available Structures