Table 4. Dissociation constants for wild-type and mutant HhaI DNA methyltransferases as determined by fluorescence quenching and ITC studies.

Enzyme	Dissociation constant, Kd (µM)
	Fluorescencea	ITC
Wild-type	4.5	6.34
F18C	0.76	ND
F18L	1.28	ND
F18Y	2.45	ND
W41I	ND	12.8
W41Y	ND	12.1

^aFluorescence measurements were not performed with the Trp41 mutants as M.HhaI has a single Trp residue, the loss of which results in decreased fluorescence.

ND, not determined.