TABLE 2.

Michaelis-Menten kinetic analysis of M. tuberculosis GlgE derivatives

Enzyme activity was monitored by detecting Pi release in triplicate and values are expressed as the mean and standard error. Quoted constants are apparent because the enzyme obeys ping-pong (substituted enzyme) kinetics (2).

	Kmapp	kcatapp	kcatapp/Kmapp
	mm	s−1	m−1 s−1
Maltohexaosea
GlgE	5.5 ± 0.5	4.3 ± 0.2	780 ± 80
GlgE_Ala	2.1 ± 0.2	0.72 ± 0.3	340 ± 40
GlgE_Asp (dimer)	1.6 ± 0.1	0.44 ± 0.01	280 ± 20
GlgE_Asp (monomer)	1.64 ± 0.05	0.216 ± 0.002	132 ± 4
GlgE-P	2.2 ± 0.2	0.053 ± 0.002	25 ± 2
M1Pb
GlgE	0.25 ± 0.03	1.25 ± 0.06	5,000 ± 600
GlgE_Ala	0.33 ± 0.07	0.59 ± 0.03	1,800 ± 400
GlgE_Asp (dimer)	0.45 ± 0.09	0.27 ± 0.01	600 ± 100
GlgE_Asp (monomer)	0.9 ± 0.2	0.15 ± 0.01	170 ± 40
GlgE-P	∼0.24c	0.020 ± 0.001d	∼80e

^a In the presence of 0.25 mm M1P.

^b Maltose 1-phosphate in the presence of 1 mm maltohexaose.

^c The GlgE-P enzyme was severely inhibited at concentrations of M1P > 1 mm with kinetics that did not adhere to simple substrate inhibition. Therefore, this value reflects the concentration of M1P that gave half the maximum observed rate.

^d This value is the maximum observed rate that was with 1 mm M1P (see footnote c above).

^e This value reflects the ratio between the maximum observed rate (footnote d) and the concentration of M1P that gave half the maximum observed rate (footnote c).