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Table 2 Active serine hydrolases in normal urine (n = 13)

From: Proteomic characterization of serine hydrolase activity and composition in normal urine

Serine hydrolase

Type

Uniprot number

MW (kDa)

Log(e)§

Potential role(s)

Kallikrein-1 (tissue kallikrein)

Protease, S1

P06870

28.889

-38.8

1. Cleaves kininogen to kinins, which act on the B1 & B2 receptor.

2. Luminal TK activates ENaC to increase Na reabsorption.

3. Luminal TK increases TRPV5 Ca reabsorption via a B2 receptor-dependent mechanism.

4. Luminal TK inhibits H+/K+ ATPase to decrease K reasbsorption.

Plasma kallikrein

Protease, S1

P03952

71.370

-5.8

1. Cleaves kininogen to kinins, which act on the B1 & B2 receptor.

Prostate specific antigen (kallikrein-3)

Protease, S1

P07288

28.741

-3.2

1. Liquefaction of semen, for sperm to move freely.

Lysosomal protective protein (cathepsin A)

Protease, S10

P10619

54.466

-57.1

1. Cleaves angiotensin I to angiotensin 1–9, which enhances the kinin effect on the B2 receptor.

Plasminogen¶

Protease, S1

P00747

90.569

-3.5

1. Luminal plasmin activates ENaC to increase Na reabsorption.

2. Luminal plasmin inhibits TRPV5 mediated Ca reabsorption.

3. Fibrinolysis

Urokinase-type plasminogen activator

Protease, S1

P00749

45.507

-38.2

1. Cleaves the zymogen plasminogen to plasmin.

2. Fibrinolysis

Prothrombin

Protease, S1

P00734

70.037

-32.4

1. Fibrinolysis

2. Function in urine unknown

Complement C1r subcomponent-like protein

Protease, S1

Q9NZP8

53.462

-81.7

1. Cleaves pro-C1s, to help activate the classical complement pathway.

Mannan binding lectin serine protease 2

Protease, S1

O00187

20.629

-28.7

1. Cleaves C2 and C4, to help activate the lectin complement pathway.

Myeloblastin (Proteinase 3)

Protease, S1

P24158

27.807

-5.2

1. Neutrophil activation

2. Cleaves human cathelicidin-18 into antimicrobial peptide LL-37.

Sialate O-acetylesterase

Carboxyl esterase

Q9HAT2

58.315

-48.6

1. Negatively regulates B cell receptor signalling – role in B cell tolerance.

2. Function in urine unknown

Bile salt-activated lipase

Type B carboxyl esterase/lipase

P19835

79.321

-128.6

1. Lipolysis

2. Function in urine unknown

S-formylgluthathione hydrolase

Esterase D

P10768

31.462

-6.6

1. Function in urine unknown

  1. Abbreviations:B1 (bradykinin 1 receptor), B2 (bradykinin 2 receptor), TK (tissue kallikrein), ENaC (epithelial sodium channel), TRPV5 (transient receptor potential channel vanilloid subtype 5), H (hydrogen), K (potassium), Na (sodium), ATP (adenosine triphosphate).
  2. §Log(e) The base-10 log of the expectation that any particular protein assignment was made at random (E-value).
  3. ¶The plasmin peptide identified was: VILGAHQEVN LEPHVQEIEV SR, which is the active serine hydrolase released the plasminogen precursor.
  4. () Alternative nomenclature.