[Relationship between the magnitude of Km and pH for L-asparaginase]

The dependency of L-asparagine hydrolysis rate on L-asparagine concentration in the presence of L-asparaginases from E. coli and Erw. carotovora is studied in a broad pH range. Km values are calculated from the data obtained. It is found that Km insignificantly depends on pH value with the pH range of 5-9 for both asparaginases. Sharp Km maximum is observed at pH greater than 9 in both cases. The maximum position does not coinside with enzyme isoelectric points and with the region of the substrate transition from zwitterionic form into anionic one.