Table 1.

Parameters for Deacetylation, Exchange, Hydrolysis and Inhibition Reactions for Pf-Sir2 with Various Substrates.

	Deacetylation			Exchangeb		Hydrolysis
	kcat	Km	Ki(NAM)a	kcat	Km	kcat	Km
	10−4 s−1	∝M	∝M	10−2 s−1	∝M	10−3 s−1	∝M
H3c	2.5 ± 0.4	372 ± 99	35 ± 2	2.5 ± 0.1	61 ± 5	1.9 ± 0.1	228 ± 28
H4c	3.5 ± 0.2	176 ± 23	NM	NM	NM	2.2 ± 0.1	137 ± 29
p300c	9.2 ± 0.5	85 ± 13	91 ± 4	6.4 ± 0.2	80 ± 7	3.4 ± 0.2	33 ± 15
NAD+d	NA	NA	NA	ND	NA	1.2 ± 0.2	NM

Conditions for measurements are described in experimental section. All reactions conducted in the presence of 400 ∝M NAD⁺.

^aK_i(NAM) is the inhibition constant for nicotinamide inhibition of deacetylation. The values are determined by varying nicotinamide (NAM) concentrations, measuring deacetylation by HPLC and plotting rate of deacetylation versus NAM concentration. Fits of points to the inhibition curve described in experimental determines the value of the parameter.

^bThe values are determined from the saturation curve for ¹⁴C-nicotinamide base-exchange.

^cPeptide primary sequence and acetylation are described in the materials and methods section. NM: Not Measured. ND: Not detected, highest concentration: 5 mM ¹⁴C-NAM.

^dNo acetylated peptide is added to these reactions. NA: Not applicable.