lactose catabolism in Psychromonas ingrahamii 37

GapMind for catabolism of small carbon sources

lactose catabolism in Psychromonas ingrahamii 37

Best path

lacP, 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 (42 with candidates)

Or see definitions of steps

Step	Description	Best candidate	2nd candidate
lacP	lactose permease LacP
lacZ	lactase (homomeric)	PING_RS10470	PING_RS14650
galK	galactokinase (-1-phosphate forming)	PING_RS10460
galT	UDP-glucose:alpha-D-galactose-1-phosphate uridylyltransferase	PING_RS10455
galE	UDP-glucose 4-epimerase	PING_RS10450	PING_RS17970
pgmA	alpha-phosphoglucomutase	PING_RS04625	PING_RS04270
glk	glucokinase	PING_RS12265	PING_RS12155
Alternative steps:
aglE'	glucose ABC transporter, substrate-binding component (AglE)	PING_RS15005
aglF'	glucose ABC transporter, permease component 1 (AglF)	PING_RS15010
aglG'	glucose ABC transporter, permease component 2 (AglG)	PING_RS15015	PING_RS10420
aglK'	glucose ABC transporter, ATPase component (AglK)	PING_RS15020	PING_RS10430
bglF	glucose PTS, enzyme II (BCA components, BglF)	PING_RS05180
crr	glucose PTS, enzyme IIA	PING_RS12590
dgoA	2-dehydro-3-deoxy-6-phosphogalactonate aldolase	PING_RS15100	PING_RS00715
dgoD	D-galactonate dehydratase	PING_RS11105	PING_RS01855
dgoK	2-dehydro-3-deoxygalactonokinase	PING_RS00720
eda	2-keto-3-deoxygluconate 6-phosphate aldolase	PING_RS15100	PING_RS00715
edd	phosphogluconate dehydratase	PING_RS01855	PING_RS11105
gadh1	gluconate 2-dehydrogenase flavoprotein subunit
gadh2	gluconate 2-dehydrogenase cytochrome c subunit	PING_RS09540
gadh3	gluconate 2-dehydrogenase subunit 3
galactonolactonase	galactonolactonase (either 1,4- or 1,5-lactone)	PING_RS10850
galdh	D-galactose 1-dehydrogenase (forming 1,4- or 1,5-lactones)	PING_RS05770	PING_RS13080
gatY	D-tagatose-1,6-bisphosphate aldolase, catalytic subunit (GatY/KbaY)
gatZ	D-tagatose-1,6-bisphosphate aldolase, chaperone subunit (GatZ/KbaZ)
gdh	quinoprotein glucose dehydrogenase	PING_RS15870	PING_RS01655
glcS	glucose ABC transporter, substrate-binding component (GlcS)
glcT	glucose ABC transporter, permease component 1 (GlcT)
glcU	glucose ABC transporter, permease component 2 (GlcU)	PING_RS15015
glcU'	Glucose uptake protein GlcU
glcV	glucose ABC transporter, ATPase component (GclV)	PING_RS10830	PING_RS10165
gnl	gluconolactonase	PING_RS10850
gtsA	glucose ABC transporter, substrate-binding component (GtsA)	PING_RS10150	PING_RS11775
gtsB	glucose ABC transporter, permease component 1 (GtsB)	PING_RS10155	PING_RS10425
gtsC	glucose ABC transporter, permease component 2 (GtsC)	PING_RS10160	PING_RS10420
gtsD	glucose ABC transporter, ATPase component (GtsD)	PING_RS10165	PING_RS10830
kguD	2-keto-6-phosphogluconate reductase	PING_RS03175
kguK	2-ketogluconokinase
kguT	2-ketogluconate transporter
klh	periplasmic 3'-ketolactose hydrolase
lacA	galactose-6-phosphate isomerase, lacA subunit	PING_RS18355
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	PING_RS03130	PING_RS06980
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	PING_RS10425	PING_RS10820
lacG	lactose ABC transporter, permease component 2	PING_RS12930	PING_RS10825
lacIIA	lactose PTS system, EIIA component
lacIIB	lactose PTS system, EIIB component
lacIIC	lactose PTS system, EIIC component
lacIICB	lactose PTS system, fused EIIC and EIIB components
lacK	lactose ABC transporter, ATPase component	PING_RS12940	PING_RS10430
lacL	heteromeric lactase, large subunit	PING_RS10470
lacM	heteromeric lactase, small subunit
lacS	lactose permease LacS
lacY	lactose:proton symporter LacY
manX	glucose PTS, enzyme EIIAB
manY	glucose PTS, enzyme EIIC
manZ	glucose PTS, enzyme EIID
MFS-glucose	glucose transporter, MFS superfamily	PING_RS08225
mglA	glucose ABC transporter, ATP-binding component (MglA)	PING_RS14490	PING_RS01830
mglB	glucose ABC transporter, substrate-binding component
mglC	glucose ABC transporter, permease component (MglC)	PING_RS01835	PING_RS14485
PAST-A	proton-associated sugar transporter A
pbgal	phospho-beta-galactosidase	PING_RS14650
ptsG	glucose PTS, enzyme IICB	PING_RS14065	PING_RS02565
ptsG-crr	glucose PTS, enzyme II (CBA components, PtsG)	PING_RS14065	PING_RS02565
SemiSWEET	Sugar transporter SemiSWEET
SSS-glucose	Sodium/glucose cotransporter
SWEET1	bidirectional sugar transporter SWEET1
tpi	triose-phosphate isomerase	PING_RS11340	PING_RS01970

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