Tài liệu Báo cáo khoa học: The crystal structure of human a-amino-b-carboxymuconatee-semialdehyde

The crystal structure of human a-amino-b-carboxymuconate￾e-semialdehyde decarboxylase in complex with

1,3-dihydroxyacetonephosphate suggests a regulatory

link between NAD synthesis and glycolysis

Silvia Garavaglia1

, Silvia Perozzi1

, Luca Galeazzi2

, Nadia Raffaelli2 and Menico Rizzi1

1 DiSCAFF Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, University of Piemonte Orientale ‘A. Avogadro’,

Novara, Italy

2 Department of Molecular Pathology and Innovative Therapies, Section of Biochemistry, Universita` Politecnica delle Marche, Ancona, Italy

Introduction

In humans, tryptophan at a level that exceeds the basal

requirements for protein and serotonin synthesis is oxi￾datively degraded through the kynurenine pathway,

producing the highly unstable intermediate a-amino￾b-carboxymuconate-e-semialdehyde (ACMS) [1]. As

shown in Fig. 1, ACMS can be either non-enzymati￾cally converted into quinolinic acid (QA), fuelling

NAD biosynthesis, or transformed by the action of

ACMS decarboxylase (ACMSD, also known as picoli￾nate carboxylase; EC 4.1.1.45) into a-aminomuconic

Keywords

cerebral malaria; kynurenine pathway;

metal-dependent amidohydrolase; NAD

biosynthesis; neurological disorders

Correspondence

M. Rizzi, DiSCAFF, University of Piemonte

Orientale, Via Bovio 6, 28100 Novara, Italy

Fax: +39 0321 375821

Tel: +39 0321 375712

E-mail: [email protected]

Database

The atomic coordinates and structure

factors of hACMSD have been deposited

with the Protein Data Bank (http://

www.rcsb.org) with accession codes 2wm1

and r2wm1, respectively

(Received 1 July 2009, revised 8 September

2009, accepted 10 September 2009)

doi:10.1111/j.1742-4658.2009.07372.x

The enzyme a-amino-b-carboxymuconate-e-semialdehyde decarboxylase

(ACMSD) is a zinc-dependent amidohydrolase that participates in picolinic

acid (PA), quinolinic acid (QA) and NAD homeostasis. Indeed, the enzyme

stands at a branch point of the tryptophan to NAD pathway, and deter￾mines the final fate of the amino acid, i.e. transformation into PA, com￾plete oxidation through the citric acid cycle, or conversion into NAD

through QA synthesis. Both PA and QA are key players in a number of

physiological and pathological conditions, mainly affecting the central ner￾vous system. As their relative concentrations must be tightly controlled,

modulation of ACMSD activity appears to be a promising prospect for the

treatment of neurological disorders, including cerebral malaria. Here we

report the 2.0 A˚ resolution crystal structure of human ACMSD in complex

with the glycolytic intermediate 1,3-dihydroxyacetonephosphate (DHAP),

refined to an R-factor of 0.19. DHAP, which we discovered to be a potent

enzyme inhibitor, resides in the ligand binding pocket with its phosphate

moiety contacting the catalytically essential zinc ion through mediation of

a solvent molecule. Arg47, Asp291 and Trp191 appear to be the key resi￾dues for DHAP recognition in human ACMSD. Ligand binding induces a

significant conformational change affecting a strictly conserved Trp–Met

couple, and we propose that these residues are involved in controlling

ligand admission into ACMSD. Our data may be used for the design of

inhibitors with potential medical interest, and suggest a regulatory link

between de novo NAD biosynthesis and glycolysis.

Abbreviations

ACMS, a-amino-b-carboxymuconate-e-semialdehyde; ACMSD, a-amino-b-carboxymuconate-e-semialdehyde decarboxylase; DHAP,

1,3-dihydroxyacetonephosphate; PA, picolinic acid; QA, quinolinic acid.

FEBS Journal 276 (2009) 6615–6623 ª 2009 The Authors Journal compilation ª 2009 FEBS 6615