When the purified L-UK was further separated by prepalative isoelectric-focusing electrophoresis, three forms different in pI values (9.9, 8.9 and 8.35) could be obtained. The chemical compositions and some other molecular and kinetic parameters (using benzoyl-L-valyl-glycyl-L-arginine-p-nitroanilide (BVGANA) or plasminogen as substrate) of the multiforms of L-UK were assessed and compared. From these data, several valuable findings were obtained as follows: 1) Although the total number of acidic amino acid residues was 1.1 to 1.2 fold larger than the sum of basic amino acid residues, the high pI values of L-UK forms (8.4 to 9.9) suggested the presence of acidic amino acid in their amide form in a large proportion. 2) The difference in pIs of the different L-UK forms was mainly due to the difference in sialic acid content. 3) Glucose (or sucrose) was found in the resolved L-UK forms but not in the original L-UK unresolved. It indicated that sugar might be adsorbed onto the enzyme molecule in a low ionic strength and high sugar content medium. 4) A sugar content pattem (but not amino acid content) distinctly different from those published by others was obtained. This discrepancy might be due to the difference in the sources of enzyme preparations. 5) The similarity in the kinetic parameters suggested that the different forms of L-UK have a similar affinity toward the substrate uscd (BVGANA and plasminogen).
嘉南學報 9, A49
轉載自 Proc. Natl. Sci. Counc. B. ROC, 7(2), 143-150 (1983)