MMAB

Chr 12

metabolism of cobalamin associated B

Also known as: ATR, CFAP23, cblB, cob

NCBI Gene: 326625ENSG00000139428UniProt: Q96EY8

This gene encodes a protein that catalyzes the final step in the conversion of vitamin B(12) into adenosylcobalamin (AdoCbl), a vitamin B12-containing coenzyme for methylmalonyl-CoA mutase. Mutations in the gene are the cause of vitamin B12-dependent methylmalonic aciduria linked to the cblB complementation group. Alternatively spliced transcript variants have been found. [provided by RefSeq, Apr 2011]

GeneReviewsResearchGenerating clinical summary…

Primary Disease Associations & Inheritance

UniProtMethylmalonic aciduria, cblB type

Clinical highlights

Gene-disease validity (ClinGen)
methylmalonic aciduria, cblB type · ARDefinitivesufficient evidence for diagnostic panels
Interpreting a novel variant
Loss of function is the curated mechanism (Gene2Phenotype), though the gene is not strongly LoF-constrained in the population — weigh truncating variants against that tolerance.Curated gene-level mechanism — a prior for triage, not a per-variant call.
0
Active trials
12
Pubs (1 yr)
—
P/LP submissions
—
P/LP missense
0.88
LOEUF
LOF
Mechanism· G2P
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GeneReview available — MMAB
Authoritative clinical overview · Recommended first read
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Some data sources returned errors (1)

omim: Error: OMIM fetch failed: 429

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD
Tolerant — LoF & missense variants common in population
LoF Constraint?
0.88LOEUF
pLI 0.004
Z-score 1.88
OE 0.45 (0.24–0.88)
Tolerant

Typical tolerance to LoF variation

Missense Constraint?
-0.11Z-score
OE missense 1.03 (0.90–1.17)
152 obs / 148.3 exp
Tolerant

Tolerant to missense variation

Observed / Expected Ratios?
LoF OE?0.45 (0.24–0.88)
0≤0.351.4
Missense OE?1.03 (0.90–1.17)
0≤0.61.4
Synonymous OE?1.07
0≤1.21.6
LoF obs/exp: 6 / 13.4Missense obs/exp: 152 / 148.3Syn Z: -0.45

ClinVar Variant Classifications

0 submitted variants in ClinVar

ClinVar

Protein Context — Lollipop Plot

MMAB · protein map & ClinVar variants

Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.

Clinical Trials

Active and recruiting trials from ClinicalTrials.gov

ClinicalTrials.gov

No active trials found for this gene.

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External Resources

Links to major genomics databases and tools

Franklin by Genoox
AI-powered variant curation and clinical analysis
DECIPHER
Genomic variants and phenotypes in rare disease patients