BAAT

Chr 9AR

bile acid-CoA:amino acid N-acyltransferase

Also known as: BACAT, BACD1, BAT, FHCA3, HCHO

NCBI Gene: 570 ENSG00000136881 UniProt: Q14032

The protein encoded by this gene is a liver enzyme that catalyzes the transfer of C24 bile acids from the acyl-CoA thioester to either glycine or taurine, the second step in the formation of bile acid-amino acid conjugates. The bile acid conjugates then act as a detergent in the gastrointestinal tract, which enhances lipid and fat-soluble vitamin absorption. Defects in this gene are a cause of familial hypercholanemia (FHCA). Two transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Jul 2008]

Primary Disease Associations & Inheritance

Hypercholanemia, familial 3MIM #619232

Active trials

Pathogenic / LP

239

ClinVar variants

Pubs (1 yr)

0.0

Missense Z

1.39

LOEUF

Clinical Summary— BAAT

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Gene-Disease Validity (ClinGen)

bile acid CoA:amino acid N-acyltransferase deficiency · ARModerate

Moderate evidence — consider for supplementary testing

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Population Constraint (gnomAD)

Low constraint (pLI 0.00) — loss-of-function variants are relatively tolerated in the population.

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ClinVar Variants

40 Pathogenic / Likely Pathogenic· 135 VUS of 239 total submissions

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GeneReview available — BAAT

Authoritative clinical overview · Recommended first read

Open GeneReview ↗

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD

Tolerant — LoF & missense variants common in population

LoF Constraint?LOEUF (Loss-of-function Observed/Expected Upper bound Fraction) is the upper bound of the 90% CI for LoF OE — the preferred gnomAD v4 metric. Lower = more intolerant to LoF. LOEUF < 0.35 = highly constrained.

1.39LOEUF

pLI 0.000

Z-score 0.50

OE 0.86 (0.55–1.39)

Tolerant

Highly tolerant — LoF variants common in population

Missense Constraint?Missense Z-score: standard deviations fewer missense variants observed vs. expected. Z > 3.09 (p < 0.001) = gene does not tolerate missense variation. OE missense < 0.6 is also considered constrained.

0.01Z-score

OE missense 1.00 (0.89–1.11)

221 obs / 221.6 exp

Tolerant

Mild missense constraint

Observed / Expected Ratios?Shaded band = 90% confidence interval. Vertical tick = point estimate. Grey threshold line = gnomAD constraint cutoff for that variant class.

LoF OE?Ratio of observed to expected LoF variants. Upper CI bound (LOEUF) ≤ 0.35 = strong LoF constraint signal.0.86 (0.55–1.39)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.1.00 (0.89–1.11)

0≤0.61.4

Synonymous OE?Control metric — synonymous variants are largely neutral and expected near OE = 1.0. Significant deviation may indicate annotation issues.1.08

0≤1.21.6

LoF obs/exp: 12 / 14.0Missense obs/exp: 221 / 221.6Syn Z: -0.55

0.6840th %ile

GOF

0.4381th %ile

LOF

0.2678th %ile

The highest-scoring mechanism for this gene is dominant-negative.

DNprediction above median

Note: In-silico variant effect predictors (SIFT, PolyPhen, REVEL, CADD) may underestimate pathogenicity of missense variants in genes with GOF or DN mechanisms. Consider functional evidence and clinical context.

Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312.