decreased. At 1600 [tM the mean activities were 11167 and 18833 with standard errors

of 16.5% and 13.4% of the mean for the Fl and U3 sites, respectively.

 The 300 utM runs exhibited mean activities of 6197 and 11866 with standard

errors of 1.0% and 1.0% of the mean for the F and U3 sites, respectively. Linear graphs

at 300 utM were the most consistent, showing no apparent influence of incubation time on

site differences or individual activities (Figs 2-4a & 2-4b). Mean activity values for the

10 [tM runs were 417 and 710 with standard errors representing 5.9% and 7.8% of the

mean. This concentration represented the lowest activity difference between samples

among the range of substrate concentrations.

 Discussion

 These results demonstrate the need for the investigation of incubation time and

substrate concentration effects to ensure the validity of data in future experiments.

Enzyme activity is extremely sensitive to changes in environmental conditions, thus it is

necessary to construct the assays such that enzyme efficiency is maintained through a

range of conditions that may be encountered. The enzymes in this study were responsive

to changes in nutrient concentrations. These responses were evident in different

relationships to changes in substrate concentration and incubation time. In some cases,

different contrasts between the enriched and reference samples were observed as the

substrate concentration was altered. This may lead the investigator to assume inverse

relationships between samples, which are not necessarily reflected in the majority of

other substrate concentrations. Therefore, the most contrasting conditions must be

assayed in order to develop the most consistent substrate concentration and incubation

time in relation to changes in sample properties.