2.4.99.20	D147V	mutation has minimal effects on pH-dependence of the enzyme	
2.4.99.20	D155N	mutation eliminates the strong pH dependence of the catalyzed reactions	
2.4.99.20	D155Q	mutation eliminates the strong pH dependence of the catalyzed reactions	
2.4.99.20	D155Q	mutation preserves the strong pH dependence of the catalyzed reactions	
2.4.99.20	E146A	mutation eliminates the strong pH dependence of the catalyzed reactions	
2.4.99.20	E146G	mutation eliminates the strong pH dependence of the catalyzed reactions