Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation·2015
Pyridine borane selectively modifies proteins, enabling reductive methylation of lysine and reduction of tryptophan under specific conditions. This reagent facilitates the synthesis of proteins with reductively attached carbohydrates, preserving protein activity.
Area of Science:
Biochemistry
Protein Chemistry
Organic Chemistry
Background:
Pyridine borane is a known reagent for reductive methylation of proteins.
Previous studies reported its use for modifying amino groups and reducing tryptophan residues.
Its specificity and applications under varied conditions required further investigation.
Purpose of the Study:
To demonstrate the specificity of pyridine borane for protein modification under different reaction conditions.
To extend the application of pyridine borane to the synthesis of proteins with reductively attached carbohydrates.
To investigate reaction parameters affecting pyridine borane-mediated modifications.
Main Methods:
Selective reduction of tryptophan residues in lysozyme using pyridine borane in acidic conditions.
Reductive methylation of lysine residues in lysozyme, chicken ovomucoid, and ribonuclease using formaldehyde and pyridine borane at pH 7.0.
Covalent attachment of glucose and lactose to bovine serum albumin.
Investigation of pH, temperature, and methanol concentration effects.
Synthesis of N-alpha-acetylglucitollysine for characterization.
Main Results:
Pyridine borane selectively reduced all tryptophans in lysozyme to dihydrotryptophan without affecting other amino acids.
No cleavage of carbohydrate moieties or loss of activity was observed for ovomucoid and ribonuclease.
Nearly complete methylation of lysines was achieved in multiple proteins, retaining full activity and tryptophan integrity.
Covalent attachment of glucose and lactose to bovine serum albumin was successful.
Incremental addition of pyridine borane accelerated modification rates.
Conclusions:
Pyridine borane exhibits high specificity for protein modification based on reaction conditions.
It is a versatile reagent for both reductive methylation of lysine and selective tryptophan reduction.
This chemistry enables the synthesis of novel protein-carbohydrate conjugates with retained biological activity.
Optimized reaction conditions enhance modification efficiency and protein integrity.
