TABLE 2.

Exploration of isoleucine biosynthesis

Pathway(s)	Carbon atom analyzed	Relative abundance of indicated intact carbon fragmenta at:
		Mid-exponential phase		Early stationary phase
		f(1)	f(2) or f(2*)	f(1)	f(2) or f(2*)
Experimentalb	Ile-δb	0.31	0.69	0.32	0.68
	Ile-α	0.16	0.84	0.17	0.83
Pyruvate and threoninec	Ile-δb	0.31	0.69	0.32	0.68
	Ile-α	0.16	0.84	0.17	0.83
Pyruvated (precursors, pyruvate and acetyl-CoA)	Ile-δb	0.05	0.95	0.05	0.95
	Ile-α	0.05	0.95	0.05	0.95
Threonine (precursors, threonine and pyruvate)e	Ile-δb	0.51	0.49	0.53	0.47
	Ile-α	0.25	0.75	0.26	0.74
Glutamate (precursors, glutamate and pyruvate)f	Ile-δb	1.00	0.00	0.98	0.02
	Ile-α	0.56	0.44	0.57	0.43

^aFor the definitions of f⁽¹⁾, f⁽²⁾, and f^(2*), see Materials and Methods. f⁽²⁾ denotes fractions for Ile-δ, and f^(2*) denotes fractions for Ile-α. f⁽²⁾{Ile-α} = f⁽³⁾{Ile-α} = 0.00 (Table 1; Fig. 3). All values except the experimental values are predictions. 

^bThe fractions for Ile-γ₁ are not given since those derived from Ile-δ and Ile-γ₁ provide the same information (63). 

^cContributions of the pyruvate and threonine pathways, 44 and 56%, respectively. 

^dCalculated with equations 1 and 2. 

^eCalculated with equations 3 and 4. 

^fCalculated with equations 5 and 6.