Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Search research articles

Related Experiment Videos

Tarantula hemocyanin shows phenoloxidase activity

H Decker¹, T Rimke

¹Institute for Molecular Biophysics, University of Mainz, Welder Weg 26, D-55128 Mainz, Germany. decker@biophysik.biologie.uni-mainz.de

The Journal of Biological Chemistry

|September 25, 1998

Summary

Tarantula hemocyanin, normally an oxygen carrier, can switch to oxidase activity after proteolysis. This functional transformation occurs at the same active site, enabling new enzymatic roles.

Related Concept Videos

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Senile hair graying: H2O2-mediated oxidative stress affects human hair color by blunting methionine sulfoxide repair.

FASEB journal : official publication of the Federation of American Societies for Experimental Biology·2009

Same author

Transmission photoemission electron microscopy for lateral mapping of the X-ray absorption structure of a metalloprotein in a liquid cell.

European biophysics journal : EBJ·2008

Same author

Allergological implication of the quaternary hexameric structure of the cockroach allergen Per a 3.

Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology·2007

Same author

The molecular heterogeneity of hemocyanin: Structural and functional properties of the 4x6-meric protein of Upogebia pusilla (Crustacea).

Gene·2007

Same author

Comparison of relative renal function measured with either 99mTc-DTPA or 99mTc-EC dynamic scintigraphies with that measured with 99mTc-DMSA static scintigraphy.

International braz j urol : official journal of the Brazilian Society of Urology·2006

Same author

Structural properties, conformational stability and oxygen binding properties of Penaeus monodon hemocyanin.

Micron (Oxford, England : 1993)·2004

Area of Science:

Biochemistry
Enzymology
Structural Biology

Background:

Enzymes typically exhibit high specificity for a single reaction.
Hemocyanin, a copper protein, usually functions as an oxygen carrier in arthropods.

Purpose of the Study:

To investigate the dual functionality of tarantula hemocyanin.
To explore the mechanism of functional transformation from oxygen transport to oxidase activity.

Main Methods:

Limited proteolysis of hemocyanin using trypsin or chymotrypsin.
Analysis of enzymatic activity (monophenoloxidase and o-diphenoloxidase).
Structural analysis of active site and substrate interactions.

Main Results:

Tarantula hemocyanin (Eurypelma californicum) undergoes an irreversible functional switch to monophenoloxidase and o-diphenoloxidase activity post-proteolysis.
N-acetyldopamine is oxidized more efficiently than L-dopa or dopamine.
Proteolytic cleavage removes an N-terminal fragment containing phenylalanine, opening the active site for substrate entry.
This switch affects specific subunits (b and c) of the seven-subunit hemocyanin.

Conclusions:

Tarantula hemocyanin demonstrates remarkable functional plasticity, transitioning from oxygen transport to oxidase activity.
Proteolysis-induced conformational changes at the active site facilitate novel enzymatic functions without altering the core copper-binding site.
The study highlights a unique mechanism for enzyme functional diversification in nature.

Related Experiment Videos