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Susceptibility to proteolysis of triosephosphate isomerase from two pathogenic parasites: Characterization of an enzyme with an intact and a nicked monomer
Author(s) -
ReyesVivas Horacio,
MartínezMartínez Eduardo,
MendozaHernández Guillermo,
LópezVelázquez Gabriel,
PérezMontfort Ruy,
Tuena de GómezPuyou Marietta,
GómezPuyou Armando
Publication year - 2002
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.10179
Subject(s) - subtilisin , triosephosphate isomerase , dimer , biochemistry , proteinase k , proteolysis , protein subunit , enzyme , biology , monomer , trypanosoma brucei , chemistry , thioflavin , polymer , organic chemistry , gene , medicine , disease , pathology , alzheimer's disease
The susceptibility to subtilisin of homodimeric triosephosphate isomerase from Trypanosoma brucei (TbTIM) and Trypanosoma cruzi (TcTIM) was studied. Their amino sequence and 3D structure are markedly similar. In 36 h of incubation at a molar ratio of 4 TIM per subtilisin, TcTIM underwent extensive hydrolysis, loss of activity, and large structural alterations. Under the same conditions, only about 50% of the monomers of TbTIM were cleaved in two sites. The higher sensitivity of TcTIM to subtilisin is probably due to a higher intrinsic flexibility. We isolated and characterized TbTIM that had been exposed to subtilisin. It exhibited the molecular mass of the dimer, albeit it was formed by one intact and one nicked monomer. Its k cat with glyceraldehyde 3‐phosphate was half that of native TbTIM, with no change in K m . The intrinsic fluorescence of nicked TbTIM was red‐shifted by 5 nm. The association between subunits was not affected. The TbTIM data suggest that there are structural differences in the two monomers or that alterations of one subunit change the characteristics of the other subunit. In comparison to the action of subtilisin on TIMs from other species, the trypanosomal enzymes appear to be unique. Proteins 2002;48:580–590. © 2002 Wiley‐Liss, Inc.