Purification and Characterization of Albumin from Frog Skin of Duttaphrynus melanostictus
Following determination of trypsin inhibitory activity, a serine protease inhibitor was purified and characterized from frog Duttaphrynus melanostictus serum. It was identified as serum albumin, with molecular weight of 67 kDa (DmA-serum). Different from bovine serum albumin, DmA-serum potently inhibited trypsin with similar K i values around 1.6 × 10−7 M. No inhibitory effect on thrombin, chymotrypsin, elastase and subtilisin was observed under the assay conditions. The N-terminal amino acid is EAEPHSRI. Subsequently, a protein with same N-terminal amino acid was purified from skin, termed as DmA-skin. However, DmA-skin is distinct from DmA-serum by binding of a haem b (0.5 mol/mol protein), and with low trypsin inhibitory activity. Frog albumin is distributed in frog skin and exhibited trypsin inhibitory activity, suggesting that it plays important roles in skin physiological functions, like water economy, metabolite exchange and osmoregulation, etc.
KeywordsAlbumin Skin Trypsin inhibitor Duttaphrynus melanostictus
Serum albumin of Duttaphrynus melanostictus
Skin albumin of D. melanostictus
n-Benzoyl-l-tyrosine ethyl ester
Bovine serum albumin
Eathylene diamine tetraacetic acid
Sodium dodecyl sulfate polyacrylamide gel electrophoresis
Enzyme-linked immunosorbent assay
Phosphate buffer saline
This work was supported by the grants from the National Natural Science Foundation (30700128, 30960053), and Foundation of Hainan University (hd09xm67).
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