Structure of aspartoacylase, the brain enzyme impaired in Canavan disease.

TitleStructure of aspartoacylase, the brain enzyme impaired in Canavan disease.
Publication TypeJournal Article
Year of Publication2007
AuthorsBitto E, Bingman CA, Wesenberg GE, McCoy JG, Phillips GN
JournalProc Natl Acad Sci U S A
Date Published2007 Jan 9
KeywordsAmidohydrolases, Animals, Aspartic Acid, Canavan Disease, Catalytic Domain, Child, Crystallography, X-Ray, Humans, Models, Molecular, Mutation, Missense, Protein Conformation, Protein Folding, Protein Structure, Tertiary, Rats, Recombinant Proteins, Static Electricity, Substrate Specificity, Zinc

Aspartoacylase catalyzes hydrolysis of N-acetyl-l-aspartate to aspartate and acetate in the vertebrate brain. Deficiency in this activity leads to spongiform degeneration of the white matter of the brain and is the established cause of Canavan disease, a fatal progressive leukodystrophy affecting young children. We present crystal structures of recombinant human and rat aspartoacylase refined to 2.8- and 1.8-A resolution, respectively. The structures revealed that the N-terminal domain of aspartoacylase adopts a protein fold similar to that of zinc-dependent hydrolases related to carboxypeptidases A. The catalytic site of aspartoacylase shows close structural similarity to those of carboxypeptidases despite only 10-13% sequence identity between these proteins. About 100 C-terminal residues of aspartoacylase form a globular domain with a two-stranded beta-sheet linker that wraps around the N-terminal domain. The long channel leading to the active site is formed by the interface of the N- and C-terminal domains. The C-terminal domain is positioned in a way that prevents productive binding of polypeptides in the active site. The structures revealed that residues 158-164 may undergo a conformational change that results in opening and partial closing of the channel entrance. We hypothesize that the catalytic mechanism of aspartoacylase is closely analogous to that of carboxypeptidases. We identify residues involved in zinc coordination, and propose which residues may be involved in substrate binding and catalysis. The structures also provide a structural framework necessary for understanding the deleterious effects of many missense mutations of human aspartoacylase.

Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID17194761
PubMed Central IDPMC1766406
Grant ListP50 GM64598 / GM / NIGMS NIH HHS / United States
U54 GM074901 / GM / NIGMS NIH HHS / United States
Y1-CO-1020 / CO / NCI NIH HHS / United States
Y1-GM-1104 / GM / NIGMS NIH HHS / United States