Stripped-Down Ancient Enzyme Makes ATP Without Its Key Catalytic Histidine

A simplified ancestral enzyme with no catalytic histidine and a restricted amino acid set has made ATP at about 1.5 per second (written 1.5 s^-1), roughly 7,500 times the apparent turnover number reported for short p-loop prototype polypeptides that run the same reaction. The pivot is that the headline speed matters less than what the enzyme gave up to get there: it lost the residue its family normally depends on and still built the molecule that powers cells. It matters now because it tests how little protein chemistry early life may have needed to store energy.

What the Research Found

The enzyme at the center of the study is a variant called Arc1-12KR, built from an ancestral nucleoside diphosphate kinase (NDK, an enzyme involved in nucleotide phosphorylation, the process of attaching phosphate groups to nucleotides). The paper is titled "Switching ATP-Forming Phosphoryl-Transfer Chemistry With a Restricted Set of Amino Acids." Its lead author is Sota Yagi, an Assistant Professor at Waseda, and the team includes Subrata Dasgupta and Shunsuke Tagami of RIKEN and Waseda Professor Satoshi Akanuma.

The reaction is a disproportionation, meaning one starting molecule is split into two different products. Arc1-12KR converted two molecules of adenosine diphosphate (ADP) into one molecule each of adenosine triphosphate (ATP) and adenosine monophosphate (AMP). ATP is the molecule cells use as an energy currency. HPLC analysis (high-performance liquid chromatography, a method that separates a chemical mixture into its components) confirmed that both ATP and AMP formed.

Rate: approximately 1.5 s^-1, the ATP-forming turnover rate of Arc1-12KR. A turnover rate counts how many reaction cycles one enzyme molecule completes each second, so this is about one and a half cycles per second.
Comparison: about 7,500 times the apparent turnover number reported for short p-loop prototype polypeptides catalyzing the same reaction.
Writer's arithmetic, not stated in the source: dividing 1.5 by 7,500 puts those prototype polypeptides near 0.0002 s^-1.

Because the 7,500-fold figure rests on an "apparent" turnover number from other work, it is only as firm as that baseline. The source does not report the baseline's kinetic parameters.

How the Science Works

The premise is that early proteins may have evolved when fewer amino acid types were available than modern proteins use. Akanuma framed the motivation this way: "We were interested in what happens when an ancestral enzyme is rebuilt using a reduced set of amino acids that may resemble the chemical limitations of early life." That quote comes from the Waseda University release, not from the paper itself.

To test it, the team engineered variants of the ancestral NDK with "progressively restricted amino acid repertoires." Arc1-12KR kept the overall NDK protein fold, the three-dimensional shape of the chain, even though it lacks the catalytic histidine normally required for NDK's conventional activity.

The group used several methods to characterize it. Biochemical assays, HPLC, and mass spectrometry (a technique that identifies molecules by their mass) established activity and products. X-ray crystallography (imaging a protein's atomic arrangement from the diffraction pattern of a crystal), molecular dynamics simulations (computer models of atomic motion), and mutational analyses probed structure, nucleotide binding, and possible mechanisms.

Those analyses indicated that aspartate and arginine residues, together with Mg2+ ions, "may have helped position the nucleotide molecules and facilitate this alternative phosphoryl-transfer reaction." The simulations also indicated that the proposed binding site could hold two ADP molecules, which fits the two-ADP-in, one-ATP-and-one-AMP-out stoichiometry. The authors state that the precise catalytic mechanism remains unresolved and that alternative pathways cannot be excluded.

What It Means for Patients

This is basic origin-of-life biochemistry. There is no clinical data, no therapeutic candidate, and no patient application in the source, so nobody should read it as a medical advance. Any relevance to health is indirect: the work adds to understanding of how enzymes and energy metabolism work at their most stripped-down, and ATP is the same energy currency that every living cell relies on. The authors do state one practical implication, that the findings could inform the design of artificial enzymes with reduced amino acid repertoires and minimal protein catalysts for biotechnology. That is a design-principle claim, not a product, and the source names no company or program pursuing it.

Competitive Landscape

The only comparison in the source is to short p-loop prototype polypeptides that catalyze the same ADP disproportionation reaction. (A p-loop is a phosphate-binding loop motif; here it serves as the starting design for very small, simple catalysts.) Arc1-12KR outpaces their apparent turnover number by about 7,500 times. The two approaches differ in kind: the prototypes are short peptides, while Arc1-12KR is a full ancestral enzyme fold rebuilt with a restricted alphabet.

That difference is also a reason for care. The source cites no prior work in detail and names no competing laboratories, and it does not place the result against other origin-of-life energy-metabolism models. A direct ranking of research groups is not possible from the available material.

Independent analyst commentary specifically on this announcement was not publicly available at publication time.

The Road to Clinic

There is no clinical pathway here. Arc1-12KR is a laboratory model of early metabolism, not a drug, diagnostic, or device. The source also leaves several quantities unstated: the ATP yield per reaction, the number of variants made, how many amino acid types were retained, the crystal structure resolution, and the age of the ancestral enzyme. Without those, readers cannot judge how closely the experiment resembles early-Earth chemistry.

What's Next

Akanuma summed up the implication in the Waseda release: "Our finding that a simplified ancestral enzyme can form ATP from ADP suggests that early proteins with limited amino acid compositions may have supported primitive energy metabolism." Both quotes in this article come from that release, as carried by News-Medical on October 29, 2026.

The authors add a limit. The findings "do not establish that this particular enzyme existed on early Earth," and they present it as an experimental model. The source gives no dates for the experiments and no timeline for follow-up work, so nothing about next steps can be reported as planned.

The open questions follow directly from the gaps above:

What the actual catalytic mechanism is, given that the authors call it unresolved.
Which amino acids Arc1-12KR retains, and what its name encodes.
How the 7,500-fold figure holds up against a fully specified baseline.
Whether the reaction conditions resemble those of early Earth.
How independent experts read the result.

For academic researchers working on minimal or designed enzymes, the practical takeaway is a proof of concept: a protein can lose its canonical catalytic residue and most of its amino acid alphabet and still turn over at about 1.5 s^-1 on a different reaction. That gives protein engineers a concrete benchmark to test against, and a reason to ask how few amino acid types a working catalyst really needs. A protein stripped of its signature residue still managed to make the molecule that powers every cell, which is a neat irony for an enzyme family built around a single histidine. What it does is shrink the list of things early chemistry would have had to supply, and that is a smaller claim than the headline suggests, and a more durable one.

-- Zara Velez, Emerging Technology Editor

Sources: Epa · Yorozuipsc · News-Medical, carrying the Waseda University release