Table 1. Substrate specifity for the partially purified l-gal-1-Pase activity.

	Partially purified kiwifruit enzyme		Partially purified Arabidopsis enzyme		E. coli expressed kiwifruit enzyme EST 233909
Substrate	nmol/min	%	nmol/min	%	nmol/min	%
l-Gal-1-P	0.220	100.0	0.163	100.0	1.61*	100.0
d-Gal-1-P	0.011	4.6			0.066	4.1
d-Mannose-1-P	0.008	3.3			0.059	3.7
Dihydroxyacetone phosphate	-0.001	-0.3
Fructose-1, 6-bisP	-0.001	-0.4
Fructose-1-P	-0.003	-1.3
Fructose-6-P	0.000	-0.2
Fructose-2, 6-bisP	0.020	9.8
Guanosine diphosphate	0.007	3.6
Glucose-6-P	0.000	-0.1			-0.001	0.0
Glucose-1-P	0.016	6.7
Glucose-1-6-bisP	0.002	1.0
Guanosine triphosphate	-0.004	-2.1
Mannose-6-P	-0.001	-0.3
p-Nitrophenyl phosphate	0.009	4.2	0.001	0.4	-0.014	-0.9
Phosphoglyceric acid	0.001	0.3			0.000	0.0
Phosphoglycolate	0.008	3.6	0.009	5.9
Ribose-5-P	0.003	1.5			0.014	0.9
Ribulose-1, 5-bisP	-0.003	-1.2
Sucrose-6-P	0.006	2.7	0.003	1.9	-0.001	-0.1
Trehalose-6-P	-0.001	-0.6	0.003	1.7	-0.003	-0.2
Myo-inositol-1-P					0.353	21.9*

Reactions were run in 100 mM Bis-Tris Propane buffer (pH 7.0), with 2 mM MgCl₂, and 0.5 mM phosphorylated substrate for 30 min (kiwifruit and Arabidopsis) or 11 min (E. coli) at 30°C. SEs were ≈2% of the mean for these assays. Empty positions indicate that the substrate was not assayed with that enzyme.

^*The test for alternative substrates used excess E. coli expressed enzyme in this assay to maximize sensitivity for alternative substrates, and the control rate was beyond the linear portion of the activity versus the amount of enzyme curve (data not shown). The true level of l-Gal-1-Pase activity was about three times this value. In separate measurements, we established that under saturating substrate concentration and 2 mM MgCl₂ at pH 7.0, myo-inositol-1-P was hydrolysed at 7.1% the rate of l-gal-1-P