Linked Life Data

16431280

Source:http://linkedlifedata.com/resource/pubmed/id/16431280

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
2006-1-24
pubmed:abstractText
Trypsins have high sequence similarity, although the responses of insect trypsins to chemical and natural inhibitors suggest they differ in specificities. Purified digestive trypsins from insects of four different orders were assayed with internally quenched fluorescent oligopeptides with two different amino acids at P1 (Arg/Lys) and 15 amino acid replacements in positions P1', P2', P2, and P3. The binding energy (deltaG(s), calculated from Km values) and the activation energy (deltaG(T)(double dagger), determined from kcat/Km values) were calculated. Dictyoptera, Coleoptera and Diptera trypsins hydrolyze peptides with Arg at P1 at least 3 times more efficiently than peptides with Lys at P1, whereas Lepidoptera trypsins have no preference between Arg and Lys at that position. The hydrophobicities of each subsite were calculated from the efficiency of hydrolysis of the different amino acid replacements at that subsite. The results suggested that insect trypsin subsites become progressively more hydrophobic along evolution. Apparently, this is an adaptation to resist plant protein inhibitors, which usually have polar residues at their reactive sites. Results also suggested that, at least in lepidopteran trypsins, S3, S2, S1', and S2' significantly bind the substrate ground state, whereas in the transition state only S1' and S2' do that, supporting aspects of the presently accepted mechanism of trypsin catalysis. Homology modeling showed differences among those trypsins that may account for the varied kinetic properties.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0965-1748
pubmed:author
pubmed:issnType
Print
pubmed:volume
36
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
130-40
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Substrate specificity of insect trypsins and the role of their subsites in catalysis.
pubmed:affiliation
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, 05513-970 São Paulo, Brazil.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't