5.4.99.15	Ca2+	134% relative activity at 1 mM, at 50°C in 50 mM phosphate buffer (pH 7.0)	
5.4.99.15	additional information	metal ions are not required for activity. Ca2+, K+, Mg2+, or Na+ have no activating or inhibiting effect on activity	
5.4.99.15	Na+	triggers maximum expression and activity of MTSase	
5.4.99.15	Zn2+	122% relative activity at 1 mM, at 50°C in 50 mM phosphate buffer (pH 7.0)