Table 1. Activation by fumarate and inhibition by ATP of ME2 malic enzyme assayed in a mitochondrial extract of INS-1 832/13 cells.

An extract of mitochondria was incubated in a reaction mixture in the presence of a saturating level of the enzyme substrate, malate (10 mM), and with or without the activator fumarate (5 mM) or inhibitor ATP (2 mM) added in different sequences. Sequential additions to a single cuvette are separated from the additions to other cuvettes by spaces between lines. Results show the individual rates or the mean ± SE of three replicate measurements.

Additions (Order of addition)	Malic Enzyme Rate (nmol NADPH formed/min/mg protein)
Fumarate (1)	0 (3)
Malate (2)	19.3 ± 1.6 (3)
Malate (1)	10.6
Fumarate (2)	19.1
ATP (3)	9.5
Malate (1)	10.5
ATP (2)	3.2
Fumarate (3)	11.4