Formation of stable complexes between urokinase and a human urinary component

Area of Science:

• Biochemistry
• Urology

Background:

• Urokinase (UK)-like plasminogen activator (PA) activity is present in human urine.
• The molecular forms and interactions of UK in urine are not fully characterized.

Purpose of the Study:

• To identify and characterize different species of UK-like PA activity in human urine.
• To investigate the formation and properties of UK complexes in concentrated urine.

Main Methods:

• Analysis of human urine by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and zymography.
• Incubation of radioiodinated UK with concentrated urine and analysis of complex formation.
• Treatment with serine proteinase inhibitors and assessment of enzymatic activity.

Main Results:

• Freshly voided urine contained UK forms of Mr = 52,000 and 35,000.
• Concentrated urine exhibited additional PA activity at Mr = 80,000 and 95,000.
• UK formed SDS-stable complexes with a urinary component (Mr ~40,000), resistant to heat and reduction.

Conclusions:

• Human urine contains multiple urokinase (UK)-like plasminogen activator (PA) species.
• UK forms stable complexes with a urinary component, resulting in novel PA activity forms.
• These findings suggest a complex regulatory mechanism for PA activity in urine.