RGD Reference Report - Involvement of conserved asparagine and arginine residues from the N-terminal region in the catalytic mechanism of rat liver and Trypanosoma cruzi tyrosine aminotransferases. - Rat Genome Database

Send us a Message



Submit Data |  Help |  Video Tutorials |  News |  Publications |  Download |  REST API |  Citing RGD |  Contact   

Involvement of conserved asparagine and arginine residues from the N-terminal region in the catalytic mechanism of rat liver and Trypanosoma cruzi tyrosine aminotransferases.

Authors: Sobrado, VR  Montemartini-Kalisz, M  Kalisz, HM  De La Fuente, MC  Hecht, HJ  Nowicki, C 
Citation: Sobrado VR, etal., Protein Sci. 2003 May;12(5):1039-50.
RGD ID: 1582407
Pubmed: PMID:12717026   (View Abstract at PubMed)
PMCID: PMC2323874   (View Article at PubMed Central)
DOI: DOI:10.1110/ps.0229403   (Journal Full-text)

Rat liver and Trypanosoma cruzi tyrosine aminotransferases (TATs) share over 40% sequence identity, but differ in their substrate specificities. To explore the molecular features related to these differences, comparative mutagenesis studies were conducted on full length T. cruzi TAT and N-terminally truncated rat TAT recombinant enzymes. The functionality of Arg315 and Arg417 in rat TAT was investigated for comparison with the conserved Arg292 and Arg386 in aspartate and bacterial aromatic aminotransferases (ASATs and ARATs). The rat TAT Arg315Lys variant remained fully active indicating that, as in T. cruzi TAT and contrary to subfamily Ialpha aminotransferases, this residue is not critical for activity. In contrast, the Arg417Gln variant was inactive. The catalytic relevance of the putative rat TAT active site residues Asn54 and Arg57, which are strictly conserved in TATs (Asn17 and Arg20 in T. cruzi TAT) but differ in ASATs and ARATs, was also explored. The substitutions Arg57Ala and Arg57Gln abolished enzymatic activity of these mutants. In both variants, spectral studies demonstrated that aromatic but not dicarboxylic substrates could efficiently bind in the active site. Thus, Arg57 appears to be functionally equivalent to Arg292 of ASATs and ARATs. Asn54 also appears to be involved in the catalytic mechanism of rat TAT since its exchange for Ser lowered the k(cat)/K(m) ratios towards its substrates. Mutation of the analogous residues in T. cruzi TAT also lowered the catalytic efficiencies (k(cat)/K(m)) of the variants substantially. The results imply that the mamalian TAT is more closely related to the T. cruzi TAT than to ASATs and ARATs.

Gene Ontology Annotations    Click to see Annotation Detail View

Biological Process
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
amino acid metabolic process  IDA 1582407 RGD 

Molecular Function
TermQualifierEvidenceWithReferenceNotesSourceOriginal Reference(s)
amino acid binding  IDA 1582407 RGD 
L-tyrosine:2-oxoglutarate aminotransferase activity  IDA 1582407 RGD 

Objects Annotated

Genes (Rattus norvegicus)
Tat  (tyrosine aminotransferase)


Additional Information