Inactivity of recombinant ELA2B provides a new example of evolutionary elastase silencing in humans.
BACKGROUND
The archetypal mammalian elastase (ELA1) is not expressed in the human pancreas, because evolutionary mutations suppressed transcription of the ELA1 gene.


OBJECTIVE
In this study, we tested the theory that the unique duplication of the ELA2 gene in humans might compensate for the loss of ELA1.


METHODS
Recombinant ELA2A and ELA2B were expressed in Escherichia coli, and their activity was tested on Glt-Ala-Ala-Pro-Leu-p-nitroanilide, DQ elastin and bovine milk protein.


RESULTS
Surprisingly, recombinant ELA2B was completely devoid of proteolytic activity, while ELA2A readily hydrolyzed all three test substrates. Furthermore, ELA2A formed an SDS-resistant complex with alpha1-antitrypsin, whereas ELA2B did not bind covalently to the inhibitor. Finally, chimeras and point mutations engineered between ELA2A and ELA2B revealed that multiple evolutionary mutations inactivated ELA2B.


CONCLUSIONS
The results indicate that ELA2B is not an elastase enzyme and confirm that ELA2A is the major elastase in the human pancreas.
Szepessy
Edit
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Department of Molecular and Cell Biology, Goldman School of Dental Medicine, Boston University, Boston, Mass., USA.
Sahin-Tóth
Miklós
M
D005075:Biological Evolution; D004926:Escherichia coli / Q000235:genetics; D020868:Gene Silencing / Q000502:physiology*; D006801:Humans; D008894:Milk Proteins / Q000378:metabolism; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D017354:Point Mutation / Q000502:physiology; D011994:Recombinant Proteins; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D000515:alpha 1-Antitrypsin / Q000378:metabolism
D008894:Milk Proteins; D011994:Recombinant Proteins; D000515:alpha 1-Antitrypsin; D012967:Sodium Dodecyl Sulfate; D010196:Pancreatic Elastase