Discovery: 'Shredder' enzyme might tear cells apart in severe COVID-19

 If you're wondering what makes COVID so deadly, scientists have discovered on enzyme that could be the cause. Here's the story from LIVESCIENCE.

(Image; Coronavirus. Credit: news.arizona.edu)

'Shredder' enzyme might tear cells apart in severe COVID-19 

LIVESCIENCE August 25, 2021 

An enzyme that can tear cell membranes to shreds may contribute to the organ damage that ultimately kills some people with severe COVID-19, a new study hints.

The enzyme, called "secreted phospholipase A2 Group IIA" (sPLA2-IIA), normally protects the body from invaders, such as bacteria, by grabbing hold of specific fats in the microbes' membranes and tearing them apart, said senior author Floyd Chilton, a biochemist and director of the Precision Nutrition and Wellness Initiative at the University of Arizona. Human cells also contain these fats, but unlike bacteria, human cells carry these fat molecules on the inner lining of their cell membranes, rather than on the outer surface.

Cells need energy to maintain the structure of their cell membranes, but when cells begin to die due to infection or stress, the fatty molecules that sPLA2-IIA targets can become exposed, leaving human cells vulnerable to attack. In addition, damaged cells release their mitochondria, the so-called powerhouse of the cell; mitochondria resemble bacteria in terms of their membrane structure, so sPLA2-IIA rushes in to shred the free-floating mitochondria to bits and spill their contents out into the body, Chilton said. This, in turn, can call the immune system into action and set off a wave of intense inflammation, according to a 2020 report in the journal EMBO Reports.

"Once that begins to happen, you're going down a slippery slope," Chilton told Live Science.

The new research from Chilton and his colleagues hints that this disastrous chain of events may unfold in patients with severe COVID-19 infections — although we'll need more research to know for sure. For now, the study only shows a strong correlation between sPLA2-IIA and the risk of severe illness and death from COVID-19; it cannot prove that the enzyme directly causes the observed damage, Chilton said.

In the study, published Tuesday (Aug. 24) in the Journal of Clinical Investigation, the researchers analyzed blood samples from 127 patients who had been hospitalized between January and July 2020. Of those patients, 30 died of COVID-19; 30 experienced a severe case but survived; and 30 patients experienced mild COVID-19 infections, meaning they didn't require supplemental oxygen. The remaining 37 people did not have COVID-19 and served as a comparison group.