Chemistry in a microenvironment of low pH, generated with the aid of an immobilized proteinase.
alpha-Chymotrypsin, when immobilized in a collodion membrane, exhibits high activity and remarkable stability. When the immobilized proteinase is exposed to 15 mM ethyl N-acetyl-L-tyrosinate in dilute pH 8.5 buffer it generates a microenvironment which, indicator studies suggest, has an effective pH of approximately 4. The presence of this locally highly acidic region produces a marked increase in the rate of hydrolysis of BzPheal = Ala dissolved in the buffer solution (BzPheal = Ala is the acylhydrazide obtained from the reaction between N-benzoyl-L-phenylalaninal and N-acetyl-L-alanine hydrazide). The observed rate is 10-times greater than in comparable control experiments incorporating a concentrated buffer solution, in which a pH-gradient does not form. The enhanced hydrolysis rate is quantitatively explained if it is attributed to the approximately 20 microliters of pH 4 solution within the membrane. Other experimental data are also consistent with this hypothesis.
Silver
M S
MS
Department of Chemistry, Amherst College, MA 01002.
Haskell
J H
JH
D000409:Alanine / Q000031:analogs & derivatives / Q000378:metabolism; D002021:Buffers; D055598:Chemical Phenomena; D002621:Chemistry; D002918:Chymotrypsin / Q000378:metabolism*; D003101:Collodion; D004058:Diffusion; D004800:Enzymes, Immobilized / Q000378:metabolism*; D006834:Hydrazines / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D010649:Phenylalanine / Q000031:analogs & derivatives; D011355:Prodrugs; D012996:Solutions; D014443:Tyrosine / Q000031:analogs & derivatives / Q000494:pharmacology
D002021:Buffers; D004800:Enzymes, Immobilized; D006834:Hydrazines; D011355:Prodrugs; D012996:Solutions; C064592:BzPheal-Ala; D014443:Tyrosine; D010649:Phenylalanine; D003101:Collodion; C053764:benzoylphenylalanine; C025787:N-acetyltyrosine; D002918:Chymotrypsin; D000409:Alanine