2AAG

Crystal Structures of the Wild-type, Mutant-P1A and Inactivated Malonate Semialdehyde Decarboxylase: A Structural Basis for the Decarboxylase and Hydratase Activities

Summary for 2AAG

• Entry DOI: 10.2210/pdb2aag/pdb
• Related: 2AAJ 2AAL
• Descriptor: Malonate Semialdehyde Decarboxylase (2 entities in total)
• Functional Keywords: tautomerase superfamily; beta-alpha-beta; homotrimeric, lyase
• Biological source: Pseudomonas pavonaceae
• Total number of polymer chains: 6
• Total formula weight: 85085.77

Authors

Almrud, J.J.,Poelarends, G.J.,Johnson Jr., W.H.,Serrano, H.,Hackert, M.L.,Whitman, C.P. (deposition date: 2005-07-13, release date: 2005-11-22, Last modification date: 2024-04-03)

Primary citation

Almrud, J.J.,Poelarends, G.J.,Johnson Jr., W.H.,Serrano, H.,Hackert, M.L.,Whitman, C.P.
Crystal Structures of the Wild-Type, P1A Mutant, and Inactivated Malonate Semialdehyde Decarboxylase: A Structural Basis for the Decarboxylase and Hydratase Activities
Biochemistry, 44:14818-14827, 2005

PubMed Abstract: Malonate semialdehyde decarboxylase (MSAD) from Pseudomonas pavonaceae 170 is a tautomerase superfamily member that converts malonate semialdehyde to acetaldehyde by a mechanism utilizing Pro-1 and Arg-75. Pro-1 and Arg-75 have also been implicated in the hydratase activity of MSAD in which 2-oxo-3-pentynoate is processed to acetopyruvate. Crystal structures of MSAD (1.8 A resolution), the P1A mutant of MSAD (2.7 A resolution), and MSAD inactivated by 3-chloropropiolate (1.6 A resolution), a mechanism-based inhibitor activated by the hydratase activity of MSAD, have been determined. A comparison of the P1A-MSAD and MSAD structures reveals little geometric alteration, indicating that Pro-1 plays an important catalytic role but not a critical structural role. The structures of wild-type MSAD and MSAD covalently modified at Pro-1 by 3-oxopropanoate, the adduct resulting from the incubation of MSAD and 3-chloropropiolate, implicate Asp-37 as the residue that activates a water molecule for attack at C-3 of 3-chloropropiolate to initiate a Michael addition of water. The interactions of Arg-73 and Arg-75 with the C-1 carboxylate group of the adduct suggest these residues polarize the alpha,beta-unsaturated acid and facilitate the addition of water. On the basis of these structures, a mechanism for the inactivation of MSAD by 3-chloropropiolate can be formulated along with mechanisms for the decarboxylase and hydratase activities. The results also provide additional evidence supporting the hypothesis that MSAD and trans-3-chloroacrylic acid dehalogenase, a tautomerase superfamily member preceding MSAD in the trans-1,3-dichloropropene degradation pathway, diverged from a common ancestor but retained the key elements for the conjugate addition of water.

PubMed: 16274229
DOI: 10.1021/bi051383m

Experimental method

X-RAY DIFFRACTION (1.85 Å)