Structure of the E. coli agmatinase, SPEB

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Agmatine amidinohydrolase (agmatinase) is vital for polyamine biosynthesis and agmatine regulation.
• This enzyme is conserved across diverse life forms.

Purpose of the Study:

• To determine the high-resolution X-ray crystal structure of E. coli agmatinase (SPEB).
• To elucidate the structural basis for agmatinase activity and mechanism.

Main Methods:

• X-ray crystallography was employed to solve the structure of E. coli SPEB.
• Structure refinement was performed, accounting for pseudomerohedral twinning.

Main Results:

• The structure revealed SPEB as a hexamer with eighteen chains in the asymmetric unit.
• Two manganese ions were identified in the active site, consistent with a dinuclear metallohydrolase fold.
• Active site residues and metal ion coordination are conserved, suggesting a shared hydrolytic mechanism with related enzymes.

Conclusions:

• The determined structure provides insights into the catalytic mechanism of agmatinase.
• The findings support a metal-activated hydrolytic mechanism involving manganese ions.