Galactoside acetyltransferase

Galactoside Acetyltransferase

Structure of Galactoside Acetyltransferase

Galactoside acetyltransferase is an enzyme that is part of the lac operon in Escherichia coli. It is encoded by the lacA gene and is responsible for the acetylation of galactosides. This enzyme plays a role in the metabolism of lactose and other galactosides by modifying them, which can affect their transport and utilization by the bacterial cell.

Function

Galactoside acetyltransferase catalyzes the transfer of an acetyl group from acetyl-CoA to the hydroxyl group of galactosides. This reaction results in the formation of acetylated galactosides, which are less likely to be substrates for the lactose permease and thus are not transported into the cell. The exact physiological role of this acetylation is not fully understood, but it is thought to prevent the accumulation of toxic galactosides within the cell.

Structure

The enzyme is a trimer, as depicted in the image on the right. Each subunit of the trimer is involved in the binding of acetyl-CoA and the galactoside substrate. The structure of galactoside acetyltransferase has been studied using X-ray crystallography, revealing details about its active site and the mechanism of acetyl transfer.

Role in the Lac Operon

The lac operon is a classic example of gene regulation in prokaryotes. It consists of three structural genes: lacZ, lacY, and lacA, which encode for beta-galactosidase, lactose permease, and galactoside acetyltransferase, respectively. The operon is regulated by the presence or absence of lactose and glucose, with the lac repressor and catabolite activator protein (CAP) playing key roles in its regulation.

Related Pages

• Lac operon
• Beta-galactosidase
• Lactose permease
• Escherichia coli
• Gene regulation