lactose catabolism in Cronobacter muytjensii ATCC 51329

GapMind for catabolism of small carbon sources

lactose catabolism in Cronobacter muytjensii ATCC 51329

Best path

lacY, lacZ, galK, galT, galE, pgmA, glk

Rules

Overview: Lactose utilization in GapMind is based on MetaCyc pathway lactose degradation II via 3'-ketolactose (link), pathway III via beta-galactosidase (link), or uptake by a PTS system followed by hydrolysis of lactose 6'-phosphate. (There is no pathway I.)

all:

lactose-transport, beta-galactosidase, galactose-degradation and glk
or lactose-PTS, pbgal, galactose-6-phosphate-degradation and glk
or lacA', lacC', lacB', klh and glucose-utilization
Comment: In pathway III, lactose is taken up and cleaved to galactose and glucose by beta-galactosidase; the glucose is consumed by kinase glk. (The galactose 1-epimerase galM, EC 5.1.3.3, is not included in galactose degradation; it is important for lactose utilization in E. coli (PMID:7966338), but not in Sinorhizobium meliloti or in Bacteroides thetaiotaomicron, which also use this pathway.) Or, a PTS forms lactose 6'-phosphate and phosphogalactosidase (pbgal) forms galactose 6-phosphate and glucose. Or, lactose is oxidized to 3'-ketolactose by a periplasmic 3-component dehydrogenase (lacACB'), and then hydrolyzed by a periplasmic enzyme (klh) to 3-keto-beta-D-galactose and D-glucopyranose, and hypothetical reduction of the 3-ketogalactose. Liberation of glucose is probably sufficient for growth.

beta-galactosidase:

lacZ
or lacL and lacM
Comment: Most lactases are homomeric, but Lactobacillus have a heteromeric enzyme LacLM. (There is also a heteromeric beta-galactosidase in barley, see BGAL_HORVU, but it is not included. Also, "evolved beta-galactosidase" ebgA from E. coli is more active with its partner ebgC, but it retains activity on its own, so it is included in step lacZ instead.)

glucose-utilization:

glucose-transport and glk
or glucose-PTS
or gdh, gnl, gadh1, gadh2, gadh3, kguT, kguK, kguD, edd and eda
Comment: Glucose can be taken up and then phosphorylated to glucose 6-phosphate by the kinase glk. Or, both uptake and phosphorylation are catalyzed by a PTS system. Or, glucose is oxidized to glucono-1,5-lactone in the periplasm (by gdh), hydrolyzed to gluconate (by gnl), oxidized to 2-ketogluconate (by gadh123), taken up by kguT, phosphorylated to 2-dehydro-6-phosphogluconate (by kguK), reduced to gluconate 6-phosphate (by kguD), dehydrated by edd to 2-dehydro-3-deoxy-gluconate 6-phosphate, and cleaved by aldolase eda to pyruvate and D-glyceraldehyde 3-phosphate.

glucose-PTS:

ptsG-crr
or bglF
or ptsG and crr
or manX, manY and manZ

glucose-transport:

MFS-glucose
or SSS-glucose
or glcU'
or PAST-A
or SemiSWEET
or SWEET1
or mglA, mglB and mglC
or gtsA, gtsB, gtsC and gtsD
or glcS, glcT, glcU and glcV
or aglE', aglF', aglG' and aglK'
Comment: Transporters and PTS systems were analyzed uzing query: transporter:glucose:D-glucose:D-glucopyranose:ALPHA-GLUCOSE:GLC:CPD-15374

galactose-degradation:

galK, galT, galE and pgmA
or galdh, galactonolactonase, dgoD, dgoK and dgoA
Comment: In the Leloir pathway, galactokinase (galK) forms galactose 1-phosphate, a uridyltransferase (galT) uses glucose 1-phosphate to form UDP-galactose, an epimerase (galE) forms UDP-glucose, and this is converted to glucose 1-phosphate by the same uridyltransferase. (We initially included the 1-epimerase galM, EC 5.1.3.3, in our model of the Leloir pathway, but found that in most bacteria, galM proteins were not important for fitness during growth on galactose; the only exception was Echvi_0697.) The oxidative pathway begins with oxidation to a lactone (by galdh) and hydrolysis to galactonate; galactonate is then dehydrated, phosphorylated, and cleaved by an aldolase.

galactose-6-phosphate-degradation: lacA, lacB, lacC, tag16P-aldolase and tpi

Comment: The tagatose 6-phosphate pathway involves the isomerization of galactose 6-phosphate to tagatose-6-phosphate (by lacAB), phosphorylation to tagatose 1,6-bisphosphate (by lacC), and an aldolase.

tag16P-aldolase:

lacD
or gatY and gatZ
Comment: Two forms of D-tagatose-1,6-phosphate aldolase are known, homomeric (lacD) or heteromeric (gatYZ or kbaYZ)

lactose-PTS:

lacIIA, lacIIB and lacIIC
or lacIIA and lacIICB
Comment: PTS systems forming lactose 6'-phosphate. Klebsiella pneumoniae has a EIIA,B,C in three separate proteins. The other characterized PTS systems have EIIA and EIICB

lactose-transport:

lacE, lacF, lacG and lacK
or lacP
or lacS
or lacY
Comment: Transporters and PTS systems were identified using query: transporter:lactose:alpha-lactose:CPD-15971

74 steps (48 with candidates)

Or see definitions of steps

Step	Description	Best candidate	2nd candidate
lacY	lactose:proton symporter LacY	AFK63_RS17735	AFK63_RS14145
lacZ	lactase (homomeric)	AFK63_RS14150	AFK63_RS15720
galK	galactokinase (-1-phosphate forming)	AFK63_RS12385
galT	UDP-glucose:alpha-D-galactose-1-phosphate uridylyltransferase	AFK63_RS12380
galE	UDP-glucose 4-epimerase	AFK63_RS12375	AFK63_RS07400
pgmA	alpha-phosphoglucomutase	AFK63_RS12645	AFK63_RS05410
glk	glucokinase	AFK63_RS04170	AFK63_RS13765
Alternative steps:
aglE'	glucose ABC transporter, substrate-binding component (AglE)
aglF'	glucose ABC transporter, permease component 1 (AglF)
aglG'	glucose ABC transporter, permease component 2 (AglG)	AFK63_RS00735
aglK'	glucose ABC transporter, ATPase component (AglK)	AFK63_RS00750	AFK63_RS12950
bglF	glucose PTS, enzyme II (BCA components, BglF)	AFK63_RS12200	AFK63_RS15680
crr	glucose PTS, enzyme IIA	AFK63_RS04050	AFK63_RS12700
dgoA	2-dehydro-3-deoxy-6-phosphogalactonate aldolase	AFK63_RS06680	AFK63_RS18255
dgoD	D-galactonate dehydratase	AFK63_RS18250	AFK63_RS08500
dgoK	2-dehydro-3-deoxygalactonokinase	AFK63_RS18260	AFK63_RS19515
eda	2-keto-3-deoxygluconate 6-phosphate aldolase	AFK63_RS06680	AFK63_RS18255
edd	phosphogluconate dehydratase	AFK63_RS06675	AFK63_RS17410
gadh1	gluconate 2-dehydrogenase flavoprotein subunit
gadh2	gluconate 2-dehydrogenase cytochrome c subunit	AFK63_RS09155
gadh3	gluconate 2-dehydrogenase subunit 3
galactonolactonase	galactonolactonase (either 1,4- or 1,5-lactone)	AFK63_RS03220
galdh	D-galactose 1-dehydrogenase (forming 1,4- or 1,5-lactones)	AFK63_RS08915	AFK63_RS02425
gatY	D-tagatose-1,6-bisphosphate aldolase, catalytic subunit (GatY/KbaY)	AFK63_RS16175
gatZ	D-tagatose-1,6-bisphosphate aldolase, chaperone subunit (GatZ/KbaZ)	AFK63_RS16180
gdh	quinoprotein glucose dehydrogenase	AFK63_RS14770	AFK63_RS14030
glcS	glucose ABC transporter, substrate-binding component (GlcS)
glcT	glucose ABC transporter, permease component 1 (GlcT)
glcU	glucose ABC transporter, permease component 2 (GlcU)
glcU'	Glucose uptake protein GlcU
glcV	glucose ABC transporter, ATPase component (GclV)	AFK63_RS12950	AFK63_RS11865
gnl	gluconolactonase	AFK63_RS03220
gtsA	glucose ABC transporter, substrate-binding component (GtsA)
gtsB	glucose ABC transporter, permease component 1 (GtsB)
gtsC	glucose ABC transporter, permease component 2 (GtsC)	AFK63_RS15730	AFK63_RS07740
gtsD	glucose ABC transporter, ATPase component (GtsD)	AFK63_RS08010	AFK63_RS12950
kguD	2-keto-6-phosphogluconate reductase	AFK63_RS19350	AFK63_RS18235
kguK	2-ketogluconokinase	AFK63_RS19360	AFK63_RS16135
kguT	2-ketogluconate transporter	AFK63_RS19355	AFK63_RS18240
klh	periplasmic 3'-ketolactose hydrolase
lacA	galactose-6-phosphate isomerase, lacA subunit
lacA'	periplasmic lactose 3-dehydrogenase, LacA subunit
lacB	galactose-6-phosphate isomerase, lacB subunit
lacB'	periplasmic lactose 3-dehydrogenase, cytochrome c component (LacB)
lacC	D-tagatose-6-phosphate kinase	AFK63_RS19050	AFK63_RS10075
lacC'	periplasmic lactose 3-dehydrogenase, LacC subunit
lacD	D-tagatose-1,6-bisphosphate aldolase (monomeric)
lacE	lactose ABC transporter, substrate-binding component
lacF	lactose ABC transporter, permease component 1	AFK63_RS02450	AFK63_RS07735
lacG	lactose ABC transporter, permease component 2
lacIIA	lactose PTS system, EIIA component	AFK63_RS16920	AFK63_RS01695
lacIIB	lactose PTS system, EIIB component	AFK63_RS16915	AFK63_RS01705
lacIIC	lactose PTS system, EIIC component	AFK63_RS02485	AFK63_RS01700
lacIICB	lactose PTS system, fused EIIC and EIIB components	AFK63_RS15580	AFK63_RS09590
lacK	lactose ABC transporter, ATPase component	AFK63_RS15745	AFK63_RS12950
lacL	heteromeric lactase, large subunit	AFK63_RS14150
lacM	heteromeric lactase, small subunit
lacP	lactose permease LacP
lacS	lactose permease LacS
manX	glucose PTS, enzyme EIIAB	AFK63_RS06845
manY	glucose PTS, enzyme EIIC	AFK63_RS06840
manZ	glucose PTS, enzyme EIID	AFK63_RS06835
MFS-glucose	glucose transporter, MFS superfamily	AFK63_RS02185	AFK63_RS13820
mglA	glucose ABC transporter, ATP-binding component (MglA)	AFK63_RS05075	AFK63_RS18575
mglB	glucose ABC transporter, substrate-binding component	AFK63_RS05070	AFK63_RS19265
mglC	glucose ABC transporter, permease component (MglC)	AFK63_RS05080	AFK63_RS18580
PAST-A	proton-associated sugar transporter A
pbgal	phospho-beta-galactosidase	AFK63_RS09595	AFK63_RS02490
ptsG	glucose PTS, enzyme IICB	AFK63_RS10860	AFK63_RS02740
ptsG-crr	glucose PTS, enzyme II (CBA components, PtsG)	AFK63_RS13120	AFK63_RS02740
SemiSWEET	Sugar transporter SemiSWEET
SSS-glucose	Sodium/glucose cotransporter
SWEET1	bidirectional sugar transporter SWEET1
tpi	triose-phosphate isomerase	AFK63_RS17880	AFK63_RS02225

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.

Downloads

Candidates (tab-delimited)
Steps (tab-delimited)
Rules (tab-delimited)
Protein sequences (fasta format)
Organisms (tab-delimited)
SQLite3 databases

Related tools

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:

ublast finds a hit to a characterized protein at above 40% identity and 80% coverage, and bits >= other bits+10.
- (Hits to curated proteins without experimental data as to their function are never considered high confidence.)
HMMer finds a hit with 80% coverage of the model, and either other identity < 40 or other coverage < 0.75.

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:

ublast finds a hit at above 40% identity and 70% coverage (ignoring otherBits).
ublast finds a hit at above 30% identity and 80% coverage, and bits >= other bits.
HMMer finds a hit (regardless of coverage or other bits).

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:

our ignorance of proteins' functions,
omissions in the gene models,
frame-shift errors in the genome sequence, or
the organism lacks the pathway.

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:

the paper from 2019 on GapMind for amino acid biosynthesis
the paper from 2022 on GapMind for carbon sources
the source code
instructions for running GapMind on your computer

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

GapMind for catabolism of small carbon sources