Scientists Engineer Enzyme to Reverse Protein Aging and Remove Advanced Glycation End Products

In a landmark development for regenerative medicine and geroscience, a collaborative team of researchers has successfully engineered a first-of-its-kind enzyme capable of reversing a fundamental form of chemical aging in proteins. The study, published in the journal Nature Communications, demonstrates that it is possible to remove advanced glycation end products (AGEs) from long-lived proteins, a feat previously considered nearly impossible by the scientific community. The research was conducted by scientists from Calico Life Sciences—the biotechnology firm backed by Alphabet Inc.—alongside experts from Revel Pharmaceuticals and the University of Colorado.

For decades, the accumulation of chemical damage on proteins has been viewed as an inevitable consequence of aging. While the body possesses robust mechanisms for recycling and replacing most proteins, certain structural components, particularly those within the extracellular matrix (ECM) like collagen and elastin, must last for years or even decades. Over time, these proteins undergo non-enzymatic reactions with sugars, leading to a process known as glycation. This process eventually results in the formation of permanent, harmful modifications called AGEs. The newly engineered enzyme, dubbed CMLase, offers a potential therapeutic pathway to "clean" these aged proteins, potentially restoring tissue elasticity and reducing chronic inflammation.

The Biochemical Challenge of Protein Glycation

To understand the significance of this breakthrough, one must look at the chemistry of the extracellular matrix. The ECM is a complex scaffolding that provides structural support to cells and tissues. In tissues such as the skin, arteries, and the lenses of the eyes, proteins like collagen are exceptionally long-lived. Because they are not frequently replaced, they are sitting ducks for the Maillard reaction—the same chemical process responsible for the browning of toast.

In this reaction, glucose and other reactive sugar molecules bond spontaneously to amino acids, primarily lysine and arginine. Initially, these form reversible "Schiff bases" and "Amadori products." However, over months and years, these intermediates undergo further rearrangement into chemically stable, irreversible AGEs. These modifications are not merely aesthetic; they create physical "crosslinks" that bridge protein fibers together, making tissues stiff and brittle. Furthermore, AGEs act as ligands for the Receptor for Advanced Glycation End Products (RAGE), triggering a cascade of pro-inflammatory signals that contribute to age-related diseases, including diabetes, atherosclerosis, and neurodegeneration.

Until now, the scientific consensus was that once an AGE is formed, it cannot be removed without destroying the underlying protein. While some "AGE-breaker" drugs like Alagebrium (ALT-711) were tested in the early 2000s, they largely failed to live up to expectations in clinical trials, as they could only target specific, less stable precursors rather than the most common and persistent AGEs.

The Search for CMLase: From Bacteria to Biotherapeutic

The research team focused their efforts on a specific AGE known as $N^epsilon$-carboxymethyl-lysine (CML). CML is one of the most abundant AGEs found in the human body and serves as a primary biomarker for oxidative stress and aging. Because CML is chemically similar to the amino acid glycine, the researchers hypothesized that they could adapt a glycine oxidase enzyme to recognize and cleave the carboxymethyl group from the modified lysine, thereby restoring the protein to its original state.

The search began with a massive computational screening of over 44,000 potential enzyme candidates. Utilizing the AlphaFold protein structure database, the researchers looked for enzymes that possessed the chemical machinery to process CML but lacked structural obstructions that would prevent them from reaching a CML molecule embedded within a large, bulky protein.

Initial tests were disappointing. While a glycine oxidase from the bacterium Bacillus subtilis could process free-floating CML molecules, it was physically unable to access CML when it was part of a peptide chain. The researchers identified a specific structural barrier—the $alpha 9$ helix—that blocked the enzyme’s active site. After filtering their database for enzymes without this obstructive helix, they found a promising but weak candidate.

Harnessing Directed Evolution

To transform this weak candidate into a functional "protein-repair" tool, the scientists utilized a process called directed evolution. This technique mimics natural selection in a laboratory setting to "breed" enzymes with specific traits.

The team created a library of millions of mutated variants of their candidate enzyme. They then engineered a specialized strain of E. coli bacteria that was unable to produce its own lysine, an essential amino acid for growth. The only way these bacteria could survive was if they possessed an enzyme variant capable of stripping the carboxymethyl group off of CML to "rescue" the lysine.

Over five rigorous rounds of mutation and selection, the researchers effectively "weaponized" evolution. Each round selected for enzymes that were faster, more stable, and better at reaching CML sites within complex protein structures. The result was CMLase: a highly optimized enzyme that can effectively de-glycate proteins without damaging the protein backbone itself.

Experimental Results in Human Tissues

The most compelling evidence of the enzyme’s efficacy came from its application to naturally aged human tissues. The researchers tested CMLase on soluble proteins taken from the lens of a 64-year-old human donor. Lens proteins, or crystallins, are among the oldest proteins in the human body, as they are never replaced from birth to death. The enzyme successfully reduced the CML burden in these proteins, demonstrating its ability to work on modifications that had accumulated over six decades.

Furthermore, the team applied the enzyme to sections of aged human skin and arterial tissue. In the skin samples, CMLase reduced CML levels by 55%, bringing the chemical signature of the tissue down to levels typically seen in a 31-year-old. In the arterial samples, the enzyme reduced the CML burden by a staggering 70%.

These results are significant because arterial stiffness is a primary driver of systolic hypertension and cardiovascular disease in the elderly. If CMLase or similar enzymes can be delivered to the vascular system, they might theoretically "de-age" the arteries, restoring the flexibility lost to decades of glycation.

Chronology of the Discovery and Future Implications

The path to this discovery has been decades in the making:

• 1980s-1990s: Researchers identify AGEs as a primary cause of diabetic complications and age-related tissue stiffening.
• Early 2000s: Clinical trials for small-molecule AGE-breakers fail, leading many to believe AGE reversal is impossible.
• 2010s: The rise of geroscience and the "damage repair" paradigm (SENS) revitalizes interest in enzymatic solutions to aging.
• 2021-2024: The collaborative team utilizes AI (AlphaFold) and synthetic biology to engineer CMLase.
• 2026: Publication of the findings in Nature Communications, marking the first successful enzymatic reversal of a major AGE in human tissue.

While the study is a major milestone, experts note that several hurdles remain before this can become a medical treatment. First, CMLase is a bacterial enzyme, which means the human immune system might identify it as a foreign invader and mount an attack. Researchers will need to "humanize" the enzyme or develop delivery methods that shield it from the immune system.

Second, the study did not measure "functional rescue." While the chemical modification was removed, the researchers have yet to prove that the treated arteries actually became more flexible or that the skin regained its youthful elasticity. Finally, CML is only one type of AGE. Other modifications, such as glucosepane crosslinks, are even more physically robust and may require an entirely different set of engineered enzymes to break.

Industry and Scientific Reaction

The reaction from the scientific community has been one of cautious optimism. Dr. Kris Verburgh, a researcher in the field of longevity, noted that "this is a proof-of-concept that the ‘irreversible’ damage of aging is, in fact, a solvable engineering problem."

Representatives from Revel Pharmaceuticals, one of the partners in the study, indicated that their next steps involve expanding their library of enzymes to target other AGEs and optimizing delivery mechanisms. The involvement of Calico Life Sciences also suggests a long-term commitment to this path, as the company is known for its focus on the fundamental biology of aging.

Analysis of Broader Impacts

If the technology behind CMLase can be scaled and safely applied to humans, the implications for public health are profound. The global burden of age-related disease is largely driven by the loss of tissue function. By reversing the chemical "wear and tear" on the body’s structural proteins, medicine could move from managing the symptoms of aging to actively repairing the damage.

In the cosmetic industry, the ability to restore skin collagen to a youthful state would represent a shift from temporary fillers to actual biological rejuvenation. In the realm of cardiology, reversing the stiffening of the aorta could drastically reduce the incidence of heart failure.

This study marks a transition in geroscience from observational biology to active intervention. It validates the theory that the chemical markers of time can be erased, provided we can design the right molecular tools to do the job. The engineering of CMLase may well be remembered as the moment the "irreversibility" of aging began to crumble.