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Physarum polymalic acid hydrolase: Recombinant expression and enzyme activation
Wolfgang Mueller1, Markus Haindl, Eggehard Holler
1Biophysik und Physikalische Biochemie, Universitaet Regensburg, 93040 Regensburg, Germany.
Abstract:
As a platform for syntheses of nanoconjugates in antitumor drug delivery, polymalic acid together with its tailoring specific exohydrolase is purified from plasmodium cultures of the slime mold Physarum polycephalum, a member of the phylum myxomycota. Polymalic acid hydrolase is expressed in an inactive form that functions as a molecular adapter for polymalic acid trafficking within the plasmodium and is activated only during secretion. Activation follows specific protein tyrosine phosphorylation and dissociation from plasma membranes. Purified inactive Physarum polymalic acid hydrolase, recombinantly expressed in yeast Saccharomyces, is activated on a preparative basis by the addition of plasma membrane fragments from plasmodia of P. polycephalum. Activation of polymalic acid hydrolase and inhibition of polymalic acid synthesis by protein tyrosine phosphorylation are complementary events and could indicate a joint signal response to plasma membrane damage.
Insights
Polymalic acid and its hydrolase from slime mold are key for nanoconjugate drug delivery. Protein tyrosine phosphorylation activates the hydrolase and inhibits synthesis, suggesting a response to membrane damage.
Area of Science:
- Biochemistry
- Cell Biology
- Biotechnology
Background:
- Polymalic acid (PMA) from Physarum polycephalum is a platform for nanoconjugate synthesis in antitumor drug delivery.
- PMA is secreted via a specific exohydrolase, PMA hydrolase, which is expressed in an inactive form.
- The inactive hydrolase acts as a molecular adapter for PMA trafficking within the plasmodium.
Purpose of the Study:
- To investigate the activation mechanism of Physarum polycephalum PMA hydrolase.
- To explore the role of protein tyrosine phosphorylation in PMA hydrolase activation and PMA synthesis.
- To understand the signaling response to plasma membrane damage in P. polycephalum.
Main Methods:
- Purification of PMA and its exohydrolase from Physarum polycephalum plasmodium cultures.
- Recombinant expression of inactive Physarum PMA hydrolase in yeast Saccharomyces.
- Activation of purified inactive hydrolase using plasma membrane fragments from P. polycephalum.
Main Results:
- Physarum PMA hydrolase is activated during secretion following specific protein tyrosine phosphorylation and dissociation from plasma membranes.
- Recombinantly expressed inactive hydrolase can be activated on a preparative basis by P. polycephalum plasma membrane fragments.
- Activation of PMA hydrolase and inhibition of PMA synthesis are complementary events mediated by protein tyrosine phosphorylation.
Conclusions:
- Protein tyrosine phosphorylation is a key regulatory mechanism for PMA hydrolase activation and PMA synthesis in Physarum polycephalum.
- These phosphorylation events suggest a coordinated cellular response to plasma membrane damage.
- The findings provide insights into the biotechnological application of PMA and its hydrolase in nanoconjugate drug delivery systems.
