<Tr> <Th> Hydrophobic environment </Th> <Td> Increase pKa </Td> <Td> Decrease pKa </Td> </Tr> <Tr> <Th> Adjacent residues of like charge </Th> <Td> Increase pKa </Td> <Td> Decrease pKa </Td> </Tr> <Tr> <Th> Salt bridge (and hydrogen bond) formation </Th> <Td> Decrease pKa </Td> <Td> Increase pKa </Td> </Tr> <P> pKa can also be influenced significantly by the surrounding environment, to the extent that residues which are basic in solution may act as proton donors, and vice versa . </P>

Most enzymes catalyze several different types of reactions