October 18, 2021
I’m essential for your body and, surprisingly, a catalyst.
What molecule am I?
Image of L-Lysine

L-Lysine is one of the nine essential amino acids—essential because the human body cannot synthesize them so they must therefore be included in a healthy diet. It is one of the four common α-amino acids to have a nitrogen atom in its side chain.

In 1889, Edmund Drechsel at the University of Freiburg (Germany) isolated lysine by hydrolyzing casein, a protein found in milk. The molecule’s structure was elucidated in 1902 by Emil Fischer and Fritz Weigert at the University of Berlin; they synthesized it and compared it with the natural product.

Fortunately for humans, lysine is abundant in a wide range of high-protein foods, including red meat, some fish, eggs, cheese, and legumes. As with most amino acids, lysine’s key role in the body is the formation of proteins.

Why are we featuring lysine during National Chemistry Week? The theme for this year’s NCW is catalysis—and lysine plays a key role in a biocatalytic–organocatalytic process reported last year by Kelsey N. Stewart, Emily G. Hicks, and Dylan W. Domaille* at the Colorado School of Mines (Golden).

The researchers sought to biosynthesize value-added chemicals from renewable feedstocks by using unmodified (i.e., natural) microorganisms rather than engineered ones. They developed a process in which they combined the bacterium Gluconobacter oxidans1 and lysine as cocatalysts for the single-pot conversion of straight-chain aliphatic alcohols to α,β-unsaturated aldehydes. The reaction takes place in water under mild conditions; it is not necessary to isolate the intermediate products.

The specific role of lysine is to prevent the reaction from diverting to a simple oxidation of the starting alcohol to a carboxylic acid. The authors’ proof-of-concept reaction is the conversion of 1-butanol to 2-ethyl-2-hexenal, a chemical that is currently manufactured on a multimillion t/year scale from nonrenewable fossil-fuel feedstocks with rhodium catalysis at elevated temperature and pressure.

The authors conclude, “our study highlights that merging chemical catalysis with in situ biocatalysis is a powerful strategy to increase the complexity and breadth of products available from bioprocesses.”

1. Also known as Gluconobacter oxydans; found in spoiled (oxidized) fruit and fermented beverages.

L-Lysine hazard information

Hazard class* GHS code and hazard statement
Not a hazardous substance or mixture  

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. 


Molecule of the future

Ciprofloxacin, the Molecule of the Week for May 30, 2016, is a widely used, inexpensive, broad-spectrum antibiotic. But there’s always room for improvement. At the ACS fall 2021 national meeting, Eszter Boros and colleagues at Stony Brook University (NY) described a souped-up version of the drug, called galbofloxacin, that consists of a gallium(III)-based siderophore attached to the ciprofloxacin molecule via a serine linkage (see figure).

Harmful bacteria use siderophores to scavenge iron from their hosts. Adding the Ga(III) siderophore to ciprofloxacin causes the bacteria to imbibe gallium instead of iron, fouling up their cellular processes and ultimately killing them. The one–two punch of gallium and ciprofloxacin allows the use of lower doses of the antibiotic to control infections.

Molecule of the future

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L-Lysine fast facts

CAS Reg. No. 56-87-1
Empirical formula C6H14N2O2
Molar mass 146.19 g/mol
Appearance White crystals or powder
Melting point 224.5 °C (dec.)
Water solubility >1 kg/L
Chemical Abstract Service - a division of ACS

Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

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