Renaming Krebs

Biologists should be consistent and descriptive in our terms for biological phenomena – and phase out confusing eponymous names for good

13th December 2021 

Many years ago I recall our A level biology curriculum covered metabolic pathways that were named after various scientists: we learned about ‘the Krebs cycle’ in mitochondria and the ‘Calvin cycle’ in chloroplasts. Other eponymous pathways include those of Kennedy (acylglycerol biosynthesis) and Entner-Doudoroff (a variant of glycolysis in some prokaryotes). Then, at university, lecturers told us to use more scientifically accurate names for the major metabolic pathways. ‘Krebs’ became the tricarboxylic acid (TCA) cycle, and ‘Calvin’ became the reductive pentose phosphate (RPP) cycle.

Unfortunately, it seems that this more rational biochemical nomenclature has failed to become standard, particularly in schools and some universities. Indeed, when I was writing a textbook on photosynthesis recently as part of the RSB’s Oxford Biology Primers series, I was advised that most younger readers would not understand my references to the TCA or RPP pathways.

KrebsHans Krebs, one of the biochemists behind the TCA cycle, and (right), Melvin Calvin, one of several researchers who discovered the RPP cycle

What's in a name?

Why is this important? There are two advantages to using scientific rather than personal nomenclature. First, the scientific name is more informative and helps students remember what is being described. Second, the use of personal names is fraught with problems, especially because science tends to be a collaborative enterprise.

In the case of the TCA cycle, German-born biochemist Hans Krebs originally proposed the pathway along with his Sheffield University colleague William Johnson[1]. Although Krebs always called it the citric acid (later the TCA) cycle, other senior scientists decided to name it only after Krebs, even though many researchers had contributed to its elucidation.

The justification for naming the Calvin cycle is even less clear. While Melvin Calvin played a key role in its discovery, at least two other researchers – Andrew Benson and James Bassham – were arguably equally important. Many scientists wished to name the cycle after all three of these senior figures, but Bassham pointedly refused, saying that he would rather honour all the other members of his team instead.

Possibly because the Nobel prize for research on carbon assimilation in plants was only awarded to Calvin, the cycle was named in most textbooks after him, but the name remains controversial[2]. People have tried renaming pathways after multiple discoverers, but this leads to clumsy titles such as the Entner-Doudoroff and Calvin-Benson-Bassham pathways, which still fail to recognise all key team members.

There is an argument that personal names can help kindle an interest in the history of science, and I have no argument against names after genuine single discoverers such as Camillo Golgi (Golgi apparatus) and Marcello Malpighi (Malpighian tubules in animal kidneys).

However, sometimes these names can perpetuate an inaccurate impression that certain scientific discoveries were made by just one high-profile individual. I’m not suggesting toppling any statues here, but one way to better reflect a more inclusive scientific process would be to eliminate inappropriate personal names and revert to more descriptive monikers, at least in the case of the metabolic pathways discussed above.

Denis Murphy FRSB is Emeritus Professor of Biotechnology at South Wales University and a series editor on the RSB’s Oxford Biology Primers textbook series

1) Krebs, H. A & Johnson, W. A. The role of citric acid in intermediate metabolism in animal tissues. Enzymologia 4, 148–156 (1937). 
2) Williams, M. Calvin Cycle, Calvin-Benson Cycle or other? Plant Sci. Today blog (April 2016).