AP Biology class blog for discussing current research in Biology

Tag: Enzymes

A Friendzyme of the Environment

A team of researchers at the University of Portsmouth in England have engineered an enzyme that breaks down plastic six times faster than the previous most efficient plastic destroying enzyme. This enzyme specializes in breaking down PET, polyethylene terephthalate, the material most plastic bottles are made of. They created this by reengineering the previous enzyme, PETase, and combining it with another enzyme, MHETase, to create a ‘super enzyme’. They used a method normally utilized by companies in the biofuel industry, who combine enzymes to break down types of cellulase. Granted, it is still far too slow to be effective in breaking down the vast amounts of plastic waste we are faced with, but it is certainly a step in the right direction.

Enzymes are made of proteins which are made up of amino acids. Amino acids consist of a carboxyl group, an amino group, and a unique R group. Amino acids create chains in which carboxyl group match with amino groups, linking together using covalent peptide bonds, formed after dehydration synthesis. The chains of amino acids begin to fold and create proteins, which are the basis of almost all enzymes.

I think this issue is an important endeavor that should be funded by governments all around the world. We all share the Earth, and it is currently under threat by a number of issues, a prime example being pollution. Up to 8.8 million metric tons of plastic waste may enter the oceans every year. Some studies put the amount of seabirds that contain some form of plastic waste in their system at upwards of 90%. Plastic waste needs solutions before it makes the oceans uninhabitable for more creatures, and a mass produced enzyme may be a valid solution. The Great Pacific Garbage Patch is a large convergence of currents in the Pacific Ocean that has collected so much garbage, a large portion of which is made of plastic, that it is comparable to the size of Texas. Developing an effective enzyme that could quickly break down plastic could become a serious help to minimizing the environmental impact of the Garbage Patch.

While we cannot develop enzymes ourselves, several tips for mitigating our plastic waste are:

-Try to use aluminum cans instead of plastic bottles.

-Always recycle or reuse plastic bottles.

-Cut the holes of six pack rings before disposing so animals cannot be caught in them.

-Use metal and paper straws as a substitute for plastic straws.


File:PETase active site.png - Wikimedia Commons

^ The enzyme PETase 














Nobel Prize awarded to Researchers for Key Discoveries in Cellular Respiration

Recent findings about the change in oxygen levels in cells show new important factors about oxygen that translate to one’s well-being. William G. Kaelin Jr., Sir Peter J. Ratcliffe and Gregg L. Semenza discovered how cells can “sense and adapt to changing oxygen availability,” and are now being awarded the Nobel Prize in Physiology or Medicine. Oxygen is a crucial aspect to how a cell’s functionality. Mitochondria in cells use oxygen to aid in converting food into ATP (energy), a process known as cellular respiration.

A representation of the reaction of cell respiration.


Gregg Semenza wanted to further look into the rise of levels of the hormone erythroprotein (EPO), a response to low levels of oxygen, or hypoxia. He found that “oxygen sensing mechanisms were present in virtually all tissues, not only in the kidney cells where EPO is normally produced.” While Semenza analyzing cultured liver cells, Semenza found a protein complex that was unknown to science. He named unidentified DNA segment the “hypoxia-inducible factor (HIF).”

Over the course of 24 years, Semanza continued to explore aspects of HIF and found two different DNA-binding proteins, now named “HIF-1a and ARNT.” Researchers worked with Semanza in finding out which parts of the HIF assist in cellular respiration. While Semenza and Ratcliffe were researching regulation of EPO, Kaelin Jr. was researching von-Hippel-Lindau’s disease (VHL). Kaelin Jr.’s research showed that VHL gene “encodes a protein that prevents the onset of cancer,” and that cancer cells lacking a functional VHL gene have “abnormally high levels of hypoxia-related genes.” But when the VHL gene was reintroduced into cancer cells, “normal levels were restored.” Eventually, Kaelin Jr. and his team found that VHL needs HIF-1a for degradation at normal oxygen levels.

Kaelin Jr. and Ratcliffe both published articles that center around protein modification called prolyl hydroxylation which “allows VHL to recognize and bind to HIF-1α degradation with the help of oxygen-sensitive enzymes.” The papers also wrote that the gene activating function of HIF-1α “was regulated by oxygen-dependent hydroxylation.” The researchers now had a much clearer idea of the effects of how oxygen is sensed within cells.

These groundbreaking finds give the science world more information about how oxygen levels are regulated in cells in physiological processes. Sensing oxygen levels is important for muscles during physical exercise, as well as the generation of blood cells and strength of one’s immune system.

Enzyme Protects Against Dangers of Oxygen

Yes, you read the title correctly: Oxygen can be dangerous.

As you may (or may not) remember, Oxygen is needed for two parts of cellular respiration. 1) For the Pyruvate made in Glycolysis to enter the mitochondria for the Krebs Cycle 2) As the final electron acceptor in the electron transport chain during Chemiosmosis. If there isn’t enough oxygen around (say, you’re running and there’s not enough oxygen to go to your muscle cells), the pyruvate made in glycolysis will not enter the mitochondria, but will instead undergo fermentation, which basically turns the NADH back into NAD+ so cycle of cellular respiration can continue.

Oxygen becomes dangerous when unhealthy cells fail to undergo cellular respiration, despite plentiful oxygen and instead undergo fermentation. This leads to uncontrollable cell growth: cancer. Luckily, scientists just discovered the enzyme superoxide dimutase, or SOD1 for short, regulates cell energy and metabolism by  transmitting signals from oxygen to glucose to repress respiration. This happens through cell signaling, when SOD1 protects the enzyme Kinase-1 gamma, of CK1Y, an important key from switching from respiration to fermentation. The results of this study were published in the Journal “Cell” on January 17th.



This diagram shows how enzymes, like SOD1, work. The substrate binds to the active site of the enzyme and the enzyme either breaks the substrate in two or puts two substrates together.


The interesting thing about this study is that SOD1 is not a new discovery. Scientists have known about SOD1 since 1969, but they thought it only protected against free radicals. Researcher Valeria C. Culotta calls SOD cells “superheroes” because of their many powers: protecting against free radicles and regulating cellular respiration.

According to Vernon Anderson, PhD, the result of this study might find out why cells turn to fermentation, casing cancer and some other diseases.


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