# Genetic Approaches to Lipid Metabolism

> **NIH NIH R01** · UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN · 2022 · $620,205

## Abstract

Fatty acids are responsible for the hydrophobic barrier properties of biological membranes. Barrier quality
depends on the species of fatty acid present in the complex lipids (generally phospholipids). In the case of
bacteria the rate of fatty acid synthesis must match the growth rate of the cells. We propose to study the
regulation of the subunit composition of acetyl-CoA carboxylase, the complex enzyme responsible for synthesis
of malonyl-CoA, the building block of fatty acid synthesis. Our prior work has shown that acetyl-CoA carboxylase
is a rate limiting step in Escherichia coli fatty acid synthesis, but it remains a mystery how the stoichiometry of
the four subunits of the enzyme is determined. A difficulty in approaching this problem is that all four acetyl-CoA
carboxylase genes are essential for growth. We propose a method to bypass the essentiality to allow the
stoichiometry and growth rate control of acetyl-CoA carboxylase assembly is regulated. In addition to providing
membrane fatty acid moieties, fatty acid synthesis is required for synthesis of two key coenzymes, lipoic acid
and biotin, both of which must be covalently attached to their cognate enzyme proteins to function. Lipoic acid is
a key cofactor for both aerobic and single carbon metabolism. In our prior work we discovered the first lipoic acid
synthesis pathway, that of E. coli, and found that the cofactor is assembled on its cognate proteins, rather than
first being assembled and then attached. Assembly on site was also seen in a more complex pathway, that of
Bacillus subtilis, that required four proteins rather than the two proteins required by E. coli. The phenotypes of
B. subtilis strains blocked in lipoic acid assembly are strikingly similar to those of human patients unable to
assemble lipoylated proteins. Indeed, these similarities strongly suggest that the pathways put forth by
laboratories investigating these disorders are incorrect. We believe that one of the human proteins has an
enzyme activity that differs from that usually ascribed and have preliminary data to support this hypothesis. We
propose to determine the pathway of lipoate synthesis in humans. Biotin is required throughout biology but is
only synthesized by bacteria, archaea, fungi and plants. Although the mechanisms of the highly conserved
enzymes responsible for assembling the fused heterocyclic rings of biotin were worked out years ago, the
metabolic source of the biotin valeric acid “tail” that contributes most of the biotin carbons atoms was unknown.
Although the carbons were known to be derived from pimelic acid, a α, ω-dicarboxylic acid, the mechanism of
pimelic acid synthesis was unknown in any organism. We showed that in E. coli the pimelate moiety is made
deceiving the fatty acid synthesis pathway into making a dicarboxylic acid rather than the usual monocarboxylic
acids. This pathway seems to explain pimelate synthesis in most bacteria, but two group of bacteria use different
pathways. These ...

## Key facts

- **NIH application ID:** 10438579
- **Project number:** 5R01AI015650-46
- **Recipient organization:** UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
- **Principal Investigator:** John E. Cronan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $620,205
- **Award type:** 5
- **Project period:** 1979-01-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10438579

## Citation

> US National Institutes of Health, RePORTER application 10438579, Genetic Approaches to Lipid Metabolism (5R01AI015650-46). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10438579. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*