GapMind for catabolism of small carbon sources


citrate catabolism in Halomonas smyrnensis AAD6

Best path

tctA, tctB, tctC, acn, icd


Overview: Citrate is utilized via ATP-citrate lyase (link) or by oxidation to 2-oxoglutarate (part of the the TCA cycle, link). MetaCyc does not explicitly represent the TCA cycle as a means for catabolizing citrate, but it is expected to function under respiratory conditions. Fitness data confirms that in diverse bacteria, ATP-citrate lyase is not necessary for aerobic utilization of citrate.

20 steps (13 with candidates)

Or see definitions of steps

Step Description Best candidate 2nd candidate
tctA citrate/Na+ symporter, large transmembrane component TctA UYS_RS0206270 UYS_RS0203150
tctB citrate/Na+ symporter, small transmembrane component TctB UYS_RS0206265 UYS_RS0203155
tctC citrate/Na+ symporter, substrate-binding component TctC UYS_RS0203160
acn aconitase UYS_RS0206600 UYS_RS0200015
icd isocitrate dehydrogenase UYS_RS0213060 UYS_RS0210720
Alternative steps:
cimH citrate:H+ symporter CimH UYS_RS0200520
cit1 citrate:H+ symporter Cit1
citA citrate:H+ symporter CitA
citD citrate lyase, acyl carrier component CitD
citE citrate lyase, citryl-ACP lyase component CitE UYS_RS16865
citF citrate lyase, citrate-ACP transferase component CitF
citM citrate:cation:H+ symporter CitM
citS citrate:Na+ symporter CitS UYS_RS0200520
citT citrate:succinate antiporter CitT
citW citrate exchange transporter CitW (with lactate or acetate) UYS_RS0200520
fecB ferric citrate ABC transporter, substrate-binding component FecB
fecC ferric citrate ABC transporter, permease component 1 (FecC) UYS_RS0210480 UYS_RS0202095
fecD ferric citrate ABC transporter, permease component 2 (FecD) UYS_RS0202095 UYS_RS0202070
fecE ferric citrate ABC transporter, ATPase component FecE UYS_RS0210490 UYS_RS0210545
SLC13A5 citrate:Na+ symporter UYS_RS0207160

Confidence: high confidence medium confidence low confidence
transporter – transporters and PTS systems are shaded because predicting their specificity is particularly challenging.

This GapMind analysis is from Sep 24 2021. The underlying query database was built on Sep 17 2021.



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About GapMind

Each pathway is defined by a set of rules based on individual steps or genes. Candidates for each step are identified by using ublast (a fast alternative to protein BLAST) against a database of manually-curated proteins (most of which are experimentally characterized) or by using HMMer with enzyme models (usually from TIGRFam). Ublast hits may be split across two different proteins.

A candidate for a step is "high confidence" if either:

where "other" refers to the best ublast hit to a sequence that is not annotated as performing this step (and is not "ignored").

Otherwise, a candidate is "medium confidence" if either:

Other blast hits with at least 50% coverage are "low confidence."

Steps with no high- or medium-confidence candidates may be considered "gaps." For the typical bacterium that can make all 20 amino acids, there are 1-2 gaps in amino acid biosynthesis pathways. For diverse bacteria and archaea that can utilize a carbon source, there is a complete high-confidence catabolic pathway (including a transporter) just 38% of the time, and there is a complete medium-confidence pathway 63% of the time. Gaps may be due to:

GapMind relies on the predicted proteins in the genome and does not search the six-frame translation. In most cases, you can search the six-frame translation by clicking on links to Curated BLAST for each step definition (in the per-step page).

For more information, see:

If you notice any errors or omissions in the step descriptions, or any questionable results, please let us know

by Morgan Price, Arkin group, Lawrence Berkeley National Laboratory