Biological complexity: metabolons in cells (Introduction)

by David Turell , Friday, April 17, 2020, 22:11 (1463 days ago) @ dhw

Enzyme groups long hypothesized as active in cells:

https://www.sciencedaily.com/releases/2020/04/200416151734.htm

"For more than 40 years, scientists have hypothesized the existence of enzyme clusters, or "metabolons," in facilitating various processes within cells. Using a novel imaging technology combined with mass spectrometry, researchers at Penn State, for the first time, have directly observed functional metabolons involved in generating purines, the most abundant cellular metabolites.

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"'Our study suggests that enzymes are not haphazardly located throughout cells, but instead occur in discrete clusters, or metabolons, that carry out specific metabolic pathways," said Stephen Benkovic, Evan Pugh University Professor and Eberly Chair in Chemistry. "Not only did we find proof that metabolons exist, but we also found that this metabolon occurs near mitochondria in cancer cells."

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"In the study, the team searched for a specific kind of metabolon, called a "purinosome," that was thought to carry out "de novo purine biosynthesis," the process by which new purines -- building blocks of DNA and RNA -- are synthesized. The researchers investigated these purinosomes within HeLa cells, a cervical cancer cell line commonly used in scientific research.

"'We have shown that the de novo purine biosynthetic [DNPB] pathway is carried out by purinosomes consisting of at least nine enzymes acting together synergistically to increase their overall activity by at least by seven-fold," said Vidhi Pareek, assistant research professor, Department of Chemistry and the Huck Institutes of Life Sciences.

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"Importantly, the team found that the DNPB pathway occurs in a channeled manner and the juxtaposition of purinosomes to the mitochondria facilitates uptake of substrates generated by the mitochondria for utilization in the pathway. Channeling occurs when enzymes are located close together so that the molecules produced are quickly transferred and processed along the enzymatic pathway, restricting equilibration with the bulk cytosol.

"'Our experiment allowed us to show that the efficiency of the de novo purine biosynthetic pathway is increased by channeling and that the proximity of purinosomes near mitochondria is consequential for the pathway," said Benkovic.'"

Comment: this is an irreducibly complex designed system that God has provided to improve cellular productive efficiency, since the processes work at such high speed.