Xylose reductase from Pichia stipitis with altered coenzyme preference improves ethanolic xylose fermentation by recombinant Saccharomyces cerevisiae

Table 3 Enzyme activities and kinetic properties

Strain	XR gene	Cofactor	Specific XR activity U mg^-1 protein	K_mA μM	K_mB mM	K_iA μM	V_max U mg^-1 protein
Y-PsNative	XYL1	NADPH NADH	0.23 ± 0.06 0.10 ± 0.02	1.0 ± 0.6 28.7 ± 5.4	62.2 ± 27.7 59.2 ± 10.5	1.4 ± 1.2 25.9 ± 11.7	0.30 ± 0.05 0.21 ± 0.01
Y-PsK270M	XYL1(K270M)	NADPH NADH	0.08 ± 0.01 0.04 ± 0.01	290 ± 78.6 -	454 ± 142 -	293 ± 169 -	0.91 ± 0.09 -
Y-PsK270R	XYL1(K270R)	NADPH NADH	0.54 ± 0.02 0.32 ± 0.02	25.8 ± 9.1 62.8 ± 18.7	468 ± 151 145 ± 36.9	22.9 ± 17.6 57.4 ± 34.9	2.13 ± 0.24 0.96 ± 0.09
Y-CpXR	XYL1(C. parapsilosis)	NADPH NADH	n.d. n.d.	- -	- -	- -	- -

Specific XR activity in cell extracts from strains Y-PsNative, Y-PsK270M, Y-PsK270R and Y-CpXR in standard conditions (200 μM NAD(P)H, 350 mM xylose) and estimated kinetic parameters for NAD(P)H reduction of xylose by corresponding cell extracts. K_mA and K_mB are the Michaelis constants of NAD(P)H and xylose, respectively, K_iA is the dissociation constant of NAD(P)H and V_max is the maximum velocity.
n.d. not detected
- not determined

ISSN: 2731-3654