Figure 2. Time-course of ¹⁵N-labelled agmatine production during the incubation of whole mitochondria with [U-¹⁵N₄]arginine.

Experiments were performed with [U-¹⁵N₄]arginine (2 mM) and other metabolites as indicated under the Materials and methods section. The line shows the best fit (r²=0.87) of a single-phase exponential association [Y=Y_max*(1−e^(−kt))]. The straight line corresponds to the linear stage of the reaction (r²=0.97). ¹⁵N-labelled agmatine was determined by the product of ¹⁵N enrichment (at.% excess/100) times total amount (pmol/mg of protein). Results are expressed as means±S.D. for 4–6 independent experiments.