Synthetic metabolic engineering-a novel, simple technology for designing a chimeric metabolic pathway

Table 1 Effects of pH on enzyme activity

Buffer	pH	Specific activity (U mg^-1total protein)^a										Total protein concentration (mg ml^-1)^b
		GK	PGI	PFK	FBA	TIM	GAPN	iPGM	ENO	PK	MLDH	Total protein concentration (mg ml^-1)^b
MES	6	0.19	7.6	4.9	7.3	9.2	0.030	0.11	1.1	9.4	0.0026	8.6
MES	7	3.7	7.3	18	7.3	17	0.039	0.17	2.6	5.2	0.013	2.2
HEPES	7	2.9	2.3	8.8	6.9	13	0.036	0.20	3.1	4.5	0.019	1.7
HEPES	8	5.1	11	18	6.5	5.0	0.042	0.087	1.2	0.65	0.014	2.2
Bicine	8	4.5	16	15	4.0	2.1	0.035	0.078	1.3	1.0	0.011	2.7
Bicine	9	7.5	14	18	2.4	0.07	0.041	0.035	0.66	0.42	0.012	3.0
CHES	9	6.0	14	30	4.4	0.9	0.031	0.017	0.40	0.19	0.0095	4.1
CHES	10	2.6	6.1	10	4.6	2.3	0.0051	0.00075	0.10	0.047	0.0021	41

^a The specific enzyme activities in the crude extract of recombinant E. coli were determined under standard assay conditions (50°C) at indicated pHs.
^b The total protein concentration of the enzyme mixture (containing 0.01 U each of GK, PGI, PFK, FBA, and TIM, along with 0.02 U each of GAPN, iPGM, ENO, PK and MLDH) was estimated.

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