Table 3. ¹³C Isotope Effects on the Oxidase Activity of the DASN OxDC Variant^a.

	13(V/K) (CO2)
pH (buffer)	WT OxDC	DASN loop variantb
4.2 [1,4-bis(2-hydroxyethyl)piperazine]	1.005 ± 0.001	1.0036 ± 0.0009
5.7 (piperazine)	1.008 ± 0.001	1.006 ± 0.001

^aValues for WT OxDC have been reported previously and are included here for ease of comparison.¹⁷

^bValues are reported for 1 mM oxalate at 25 °C. Under these conditions, the decarboxylase activity of the DASN OxDC variant is negligible and the ratio of CO₂ production and O₂ consumption equals 2 (Figure 4B).