Pyrococcus abyssi alkaline phosphatase: the dimer is the active form.

Area of Science:

• Biochemistry
• Enzymology
• Structural Biology

Background:

• Alkaline phosphatases (APs) are non-specific phosphomonoesterases active under alkaline conditions.
• APs are typically homodimeric metalloenzymes, but the necessity of this quaternary structure for activity is unclear.
• Previous studies suggested Pyrococcus abyssi AP exists as both monomer and homodimer.

Purpose of the Study:

• To determine the actual quaternary structure of P. abyssi AP in solution.
• To identify factors controlling dimer assembly and dissociation.
• To elucidate the relationship between quaternary structure and AP activity.

Main Methods:

• Isolation of monomeric and dimeric forms of P. abyssi AP.
• Analysis of quaternary structure under varying pH and buffer conditions.
• Investigation of metal ion involvement in quaternary structure stability.

Main Results:

• P. abyssi AP quaternary structure is sensitive to pH, with acidic conditions favoring the monomer.
• Buffer composition influences quaternary state; potassium phosphate allows both monomer and dimer, while Tris-HCl yields only the dimer.
• Metal removal results in a monomeric form, which can be reactivated with variable efficiency.

Conclusions:

• The active form of P. abyssi AP is the homodimer.
• pH, buffer type, and bound metals are critical for maintaining the homodimeric structure.
• The monomeric form of P. abyssi AP is not enzymatically active.