TABLE 1.

Probability of ¹³C labeling of specified carbon atoms within an isoprene unit synthesized via the MEP or the MVA pathway For isoprene units obtained from [1-¹³C]- and [1,6-¹³C₂]glucose feeding, two types of carbon atoms, labeled with different probabilities (p), are expected, unlike for native and [U-¹³C₆]glucose-derived ones, where all carbon atoms are labeled with equal probability. Numbering of carbon atom positions is given in Fig. 2.

Feeding conditions	Position in isoprene unit	Isoprene unit
		MEP-derived		MVA-derived
		p probability of 13C labeling	No. of carbon atoms labeled with indicated p	p probability of 13C labeling	No. of carbon atoms labeled with indicated p
Native glucose	C-1		0.01
	C-2		all 5 atoms labeled with p = 0.01
	C-3
	C-4
	C-5
[1-13C]Glucose	C-1	0.49	2 atoms labeled with p = 0.49	0.01	3 atoms labeled with p = 0.49
	C-2	0.01	3 atoms labeled with p = 0.01	0.49	2 atoms labeled with p = 0.01
	C-3	0.01		0.01
	C-4	0.01		0.49
	C-5	0.49		0.49
[1,6-13C2]Glucose	C-1	0.98	2 atoms labeled with p = 0.98	0.01	3 atoms labeled with p = 0.98
	C-2	0.01	3 atoms labeled with p = 0.01	0.98	2 atoms labeled with p = 0.01
	C-3	0.01		0.01
	C-4	0.01		0.98
	C-5	0.98		0.98
[U-13C6]Glucose	C-1		0.99
	C-2		all 5 atoms labeled with p = 0.99
	C-3
	C-4
	C-5