PMID: 39646Jul 1, 1979

The effects of chemical modification on the refolding transition of alpha-chymotrypsin

Biophysical Chemistry
J D Stoesz, R Lumry


The role of several active site residues of alpha-chymotrypsin in the prototypical refolding transition between active and inactive forms of this enzyme is examined using chemical modification. Oxidation of Met-192 to the sulfoxide results in a derivative which remains entirely in an active state from pH 6 to 9. The derivative becomes inactive only at high pH with pKa = 10.3, delta H0 = 9.5 kcal and delta S0 = -15 eu., indicating the sulfoxide group supplies about 2.1 kcal of active state stabilization relative to the unoxidized methionine side chain. The refolding transition of N-methyl-His-57-alpha-chymotrypsin, in which a nitrogen of the "charge relay" histidine is methylated, displays one ionization process with an apparent pKa of 9.45. The absence of an additional ionization process with a pKa near 7 provides evidence that one of the ionizations in the six state mechanism which describes this transition in alpha-chymotrypsin is linked to the charge relay system. We also demonstrate, using alpha-chymotrypsin, Met-192-sulfoxide-alpha-chymotrypsin and N-methyl-His-57-alpha-chymotrypsin, that the 230 nm circular dichroism band is a quantitative probe of the active-inactive equilibrium, although the chromophore or chromophores ...Continue Reading


Nov 24, 2004·Protein Science : a Publication of the Protein Society·Janka MátraiYves Engelborghs

Related Concepts


Trending Feeds


Coronaviruses encompass a large family of viruses that cause the common cold as well as more serious diseases, such as the ongoing outbreak of coronavirus disease 2019 (COVID-19; formally known as 2019-nCoV). Coronaviruses can spread from animals to humans; symptoms include fever, cough, shortness of breath, and breathing difficulties; in more severe cases, infection can lead to death. This feed covers recent research on COVID-19.

Sexual Dimorphism in Neurodegeneration

There exist sex differences in neurodevelopmental and neurodegenerative disorders. For instance, multiple sclerosis is more common in women, whereas Parkinson’s disease is more common in men. Here is the latest research on sexual dimorphism in neurodegeneration

HLA Genetic Variation

HLA genetic variation has been found to confer risk for a wide variety of diseases. Identifying these associations and understanding their molecular mechanisms is ongoing and holds promise for the development of therapeutics. Find the latest research on HLA genetic variation here.

Super-resolution Microscopy

Super-resolution microscopy is the term commonly given to fluorescence microscopy techniques with resolutions that are not limited by the diffraction of light. Here are the latest discoveries pertaining to super-resolution microscopy.

Genetic Screens in iPSC-derived Brain Cells

Genetic screening is a critical tool that can be employed to define and understand gene function and interaction. This feed focuses on genetic screens conducted using induced pluripotent stem cell (iPSC)-derived brain cells.

Brain Lower Grade Glioma

Low grade gliomas in the brain form from oligodendrocytes and astrocytes and are the slowest-growing glioma in adults. Discover the latest research on these brain tumors here.

CD4/CD8 Signaling

Cluster of differentiation 4 and 8 (CD8 and CD8) are glycoproteins founds on the surface of immune cells. Here is the latest research on their role in cell signaling pathways.

Alignment-free Sequence Analysis Tools

Alignment-free sequence analyses have been applied to problems ranging from whole-genome phylogeny to the classification of protein families, identification of horizontally transferred genes, and detection of recombined sequences. Here is the latest research.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disease characterized by unexplained disabling fatigue; the pathology of which is incompletely understood. Discover the latest research on chronic fatigue syndrome here.