Creative Touch Permanent Makeup and Aesthetics

Coenzyme A (CoA) is not itself a structural component of skin – it is the metabolic infrastructure through which structural components are built. Every ceramide molecule in the stratum corneum, every free fatty acid in the barrier lipid matrix, every molecule of sebum secreted from a sebaceous gland, and every sterol in the epidermal membrane requires CoA-mediated acyl group transfer at one or more steps in its synthesis pathway. ^[1] CoA functions as a carrier – it accepts acyl groups from metabolic intermediates, holds them in high-energy thioester bonds, and transfers them to acceptor molecules in the synthetic reactions that build lipids, acetylate histones, and fuel the citric acid cycle. The skin synthesises its own cytosolic CoA pool from pantothenic acid (Vitamin B5) through a five-step enzymatic pathway, with a separate mitochondrial CoA pool transported across the inner mitochondrial membrane by the SLC25A42 transporter. A 2025 study from the University of Pennsylvania demonstrated that disrupting cytosolic CoA synthesis specifically in the skin depletes the very long chain ceramides essential for barrier function whilst paradoxically increasing sebum production – because the epidermis and the sebaceous gland draw on CoA through different metabolic routes and respond to its deficiency in divergent ways. ^[4] Understanding CoA is what makes the Pantothenic Acid → barrier function → acne connection a mechanistically coherent chain rather than an observed correlation.

Structure: The Thiol Group

CoA’s functional chemistry rests on a single reactive site: the free thiol group (–SH) at its terminal end, contributed by the cysteamine component of its molecular structure. The thiol group forms a high-energy thioester bond with acyl groups – activated fatty acids, acetyl units, or other organic acids – creating acyl-CoA species (fatty acyl-CoA, acetyl-CoA, succinyl-CoA, and others) that are the immediate substrates for the synthetic and oxidative reactions of lipid and energy metabolism. The thioester bond stores chemical energy that is released when the acyl group is transferred to its acceptor molecule, driving reactions that would otherwise be thermodynamically unfavourable. This makes CoA not merely a carrier but an energy-coupling agent – its involvement makes biosynthetic reactions proceed efficiently at biological temperatures and concentrations.

The full CoA molecule consists of three components assembled in sequence: adenosine 3′,5′-bisphosphate (the nucleotide anchor for enzyme recognition), pantothenic acid (the vitamin-derived component that provides the structural backbone), and cysteamine (the thiol-bearing terminal unit). All three must be present for a functional CoA molecule; this is why pantothenic acid availability is a rate-limiting determinant of total cellular CoA concentration.

Biosynthesis: From Pantothenic Acid to CoA

Coenzyme A is synthesised de novo in the cytosol through a conserved five-step enzymatic pathway that begins with pantothenic acid and requires cysteine and ATP as additional substrates: ^[1]

1. Pantothenate → 4′-phosphopantothenate – catalysed by pantothenate kinase (PANK); the rate-limiting step, and the primary regulatory control point for total cellular CoA concentration. PANK activity is feedback-inhibited by CoA itself – the pathway is autoregulated, with excess CoA slowing its own production.
2. 4′-phosphopantothenate + cysteine + ATP → 4′-phosphopantothenoylcysteine – catalysed by phosphopantothenoylcysteine synthetase (PPCS); cysteine contributes the thiol group that will become CoA’s reactive terminus.
3. 4′-phosphopantothenoylcysteine → 4′-phosphopantetheine – decarboxylation by phosphopantothenoylcysteine decarboxylase (PPCDC).
4. 4′-phosphopantetheine → dephospho-CoA – catalysed by 4′-phosphopantetheine adenyltransferase (PPAT), the first of two activities carried out by CoA synthase (COASY).
5. Dephospho-CoA → CoA – phosphorylation by dephospho-CoA kinase (DPCK), the second COASY activity, completing the molecule.

Once synthesised in the cytosol, CoA is transported across the inner mitochondrial membrane by the SLC25A42 transporter – in exchange for adenosine 3′,5′-diphosphate – establishing a separate mitochondrial CoA pool used for β-oxidation and the citric acid cycle. ^[1] The cytosolic and mitochondrial CoA pools are functionally distinct: cytosolic CoA drives anabolic lipid synthesis; mitochondrial CoA supports catabolic energy metabolism. The SLC25A42 transporter is clinically relevant – loss-of-function mutations cause a rare mitochondrial encephalomyopathy, and pantothenic acid supplementation has been shown to partially rescue CoA levels in patient fibroblasts by saturating the biosynthesis pathway upstream of the transport defect.

Acetyl-CoA: The Lipid Synthesis Hub

The most abundant and metabolically central CoA species in the cytosol is acetyl-CoA – a two-carbon acetyl unit attached to CoA via its thioester bond. Cytosolic acetyl-CoA is the universal building block for de novo fatty acid synthesis: the fatty acid synthase (FASN) complex uses acetyl-CoA as the starter unit and malonyl-CoA (derived from acetyl-CoA by the enzyme ACC) as the two-carbon extender, adding carbons iteratively to produce the saturated fatty acid chains that are the structural backbone of ceramides, phospholipids, and sebum lipids.

In the skin, cytosolic acetyl-CoA is generated primarily by ATP-citrate lyase (ACLY), which cleaves mitochondrion-derived citrate into acetyl-CoA and oxaloacetate in the cytosol and nucleus. A backup route is provided by acyl-CoA synthetase short-chain family member 2 (ACSS2), which generates acetyl-CoA directly from acetate. ^[4] Under normal conditions ACLY is the dominant cytosolic acetyl-CoA source; ACSS2 is upregulated as a compensatory mechanism when ACLY is impaired. When both are absent from skin keratinocytes simultaneously, the consequences are severe and mechanistically instructive – covered below in the divergence section.

Acyl-CoA: Ceramide and Barrier-Critical Lipid Synthesis

Fatty acid elongation beyond the C16–C18 chain lengths produced by FASN requires the activation of fatty acids to their acyl-CoA form – catalysed by acyl-CoA synthetases (including FATP4, encoded by SLC27A4) – before the elongase enzymes (ELOVL1, ELOVL3, ELOVL4) can extend them to the very long chain fatty acids (VLCFAs, ≥C20) required for skin barrier ceramide synthesis. ^[2]

The most structurally critical ceramide species in the barrier – ω-O-acylceramide – requires an ultra-long chain fatty acid (≥C28) esterified to the ω-hydroxyl group of a ceramide backbone. FATP4 activates ω-hydroxy fatty acids to their ω-OH acyl-CoA form, which CERS3 then incorporates into the ceramide via amide bond formation. The resulting ω-O-acylceramide covalently bonds to cornified envelope proteins, forming the lipid envelope that is structurally essential for barrier integrity – loss-of-function mutations in FATP4 cause ichthyosis prematurity syndrome, confirming that acyl-CoA availability in this pathway is not metabolically peripheral but barrier-critical. ^[3]

Each step in this chain – from acetyl-CoA production through ACLY, to fatty acid elongation via acyl-CoA intermediates, to ceramide assembly by CERS3 – is CoA-dependent. Disruption at any point produces barrier lipid deficiency, with the clinical presentation depending on which step is compromised.

The Epidermis vs. Sebaceous Gland Divergence

The most clinically significant recent finding in CoA skin biology is the 2025 University of Pennsylvania study (Nguyen et al., Cell Reports, PMC12010789) using inducible skin-specific double knockout (DKO) mice lacking both ACLY and ACSS2 – eliminating cytosolic acetyl-CoA synthesis capacity from skin keratinocytes entirely. ^[4]

The results revealed a striking divergence between the skin’s two major lipid-producing compartments:

Epidermis:did not restore very long chain ceramide composition – because acetyl-CoA is required specifically for fatty acid elongation, and simply providing exogenous lipids cannot substitute for the intracellular elongation capacity that CoA enables. ^[4]

Sebaceous glands: Neutral lipid staining was maintained. Sebum production was not reduced – it modestly increased. The mechanism: sebaceous glands upregulated the CD36 fatty acid transporter, enabling increased uptake of circulating fatty acids from systemic lipolysis to compensate for reduced intracellular acetyl-CoA synthesis. Olive oil supplementation further boosted sebum production via the same CD36 import route. ^[4]

This divergence is mechanistically interpretable: the epidermis requires intracellular de novo synthesis of very long chain fatty acids for barrier ceramide production – a process that cannot be substituted by importing pre-formed circulating lipids because the required ultra-long chain species are not circulating in adequate concentration. The sebaceous gland, producing sebum from shorter chain triglycerides, wax esters, and squalene (which can be supplied from circulation), is more metabolically flexible and can sustain its secretory function using imported fatty acid substrate when de novo synthesis is compromised.

Histone Acetylation and Gene Regulation

Beyond lipid synthesis, cytosolic acetyl-CoA is the acetyl group donor for histone acetyltransferases (HATs) – the enzyme family that acetylates lysine residues on histone tails, relaxing chromatin structure and enabling transcription factor access. ^[4] Histone acetylation is one of the primary mechanisms by which the differentiation state of keratinocytes is epigenetically regulated during their journey from basal stem cell to terminally differentiated corneocyte.

In keratinocytes, the differentiation programme involves progressive changes in gene expression – from the keratin 14/keratin 5 expression of basal cells, through the keratin 10/keratin 1 expression of suprabasal differentiating cells, to the loricrin and involucrin expression of the granular layer – and CoA availability influences the histone acetylation state that makes this gene expression progression possible. The 2025 ACLY DKO data showed an overlap of K14 (basal marker) and K10 (differentiation marker) expression in the same cells – consistent with disrupted differentiation programming attributable at least in part to altered histone acetylation from depleted acetyl-CoA supply. ^[4]