L-threonine catabolism in Rhodobacter maris JA276

Best path

snatA, ltaE, adh, ackA, pta, gcvP, gcvT, gcvH, lpd

Rules

Overview: L-threonine degradation in GapMind is based on MetaCyc pathway I via 2-ketobutyrate formate-lyase (link), pathway II via glycine (link), pathway III via methylglyoxal (link), and pathway IV via threonine aldolase (link). Pathway V is not thought to occur in prokaryotes and is not included.

• all:
  • threonine-transport, tdcB, tdcE and propionyl-CoA-degradation
  • or threonine-transport, tdh, kbl and glycine-degradation
  • or threonine-transport, tdh, tynA and methylglyoxal-degradation
  • or threonine-transport, ltaE, acetaldehyde-degradation and glycine-degradation
  • Comment: In L-threonine degradation I, threonine dehydratase (tdcB) forms 2-iminbutanoate, which is deaminated to 2-oxobutanoate (either by the same enzyme or by ridA); then formate-lyase (tdcE) converts this to propanoyl-CoA. (MetaCyc also includes conversion to propanoate, which forms ATP, but this does not allow for growth unless the formate can be utilized.) In L-threonine degradation II, a dehydrogenase (tdh) forms L-2-amino-3-oxobutanoate, and a C-acetyltransferase (kbl) cleaves this to acetyl-CoA and glycine. In L-threonine degradation III, tdh forms L-2-amino-3-oxobutanoate, and oxidase tynA forms methylglyoxal. In L-threonine degradation IV, aldolase ltaE cleaves threonine to acetaldehyde and glycine.
• L-lactate-degradation:
  • L-LDH
  • or lldE, lldF and lldG
  • or lutA, lutB and lutC
  • or DVU3033 and DVU3032
  • or lctO and acs
  • or lctO, ackA and pta
  • Comment: Various L-lactate dehydrogenases are known, with different numbers of subunits; these all form pyruvate. Or, after L-lactate oxidase (lctO) forms acetate, the acetate is activated to acetyl-CoA.
• methylglyoxal-degradation:
  • gloA*, gloB and D-lactate-dehydrogenase
  • or yvgN, aldA and L-lactate-degradation
  • Comment: In methylglyoxal degradation I (link), gloA condenses methylglyoxal with glutathione to (R)-S-lactoylglutathione, gloB cleaves it to D-lactate (also known as (R)-lactate) and glutathione, and the lactate is oxidized to pyruvate. In methylglyoxal degradation IV (link), yvgN reduces methylglyoxal to (S)-lactaldehyde, aldA oxidizes it to (S)-lactate (also known as L-lactate).
• D-lactate-dehydrogenase:
  • D-LDH
  • or lctB, lctC and lctD
  • or glcD, glcE and glcF
  • Comment: Acetobacterium woodii uses an electron-bifurcating dehydrogenase (lctBCD) for growth on lactate. The Km for D-lactate is far below that for L-lactate (Km of 3.6 mM vs. 112 mM; PMID:24762045), so we consider it to be a D-lactate dehydrogenase. GlcDEF from E. coli (EC 1.1.99.14) is usually described as glycolate dehydrogenase or glycolate oxidase, but it has similar activity on D-lactate (PMID:4557653), and homologs from various Proteobacteria are important for D-lactate utilization. The physiological electron acceptor is not known, so terming GlcDEF an oxidase is questionable.
• glycine-degradation:
  • glycine-reductase and ackA
  • or glycine-reductase and pta
  • or gcvP, gcvT, gcvH and lpd
  • Comment: Glycine can be reduced to acetyl phosphate by glycine reductase (EC 1.21.4.2), and then converted to acetate (by ackA in reverse) or acetyl-CoA (by pta) Or glycine can cleaved to ammonia, CO2, and 5,10-methylene-tetrahydrofolate by the glycine cleavage system, gcvPTH/lpd.
• glycine-reductase: grdA, grdE, grdB, grdD and grdC
• acetaldehyde-degradation:
  • ald-dh-CoA
  • or adh and acs
  • or adh, ackA and pta
  • Comment: Acetaldehyde can be oxidized to acetyl-CoA, or oxidized to acetate and activated to acetyl-CoA by either acetyl-CoA synthetase (acs) or by acetate kinase (ackA) and phosphate acetyltransferase (pta).
• propionyl-CoA-degradation:
  • prpC, prpD, acn and prpB
  • or prpC, acnD, prpF, acn and prpB
  • or propionyl-CoA-carboxylase, epi and methylmalonyl-CoA-mutase
  • or pco, hpcD, dddA and iolA
  • Comment: In 2-methylcitrate cycle I, propionyl-CoA is combined with oxalacetate (by prpC) to give methylcitrate, dehydrated to cis-2-methylaconitate by prpD, hydrated to (2R,3S)-2-methylisocitrate, and a lyase produces pyruvate and succinate. (We consider succinate as a central intermediate, as most organisms can activate it to succinyl-CoA or can oxidize it to fumarate and convert that to oxaloacetate.) In 2-methylcitrate cycle II, a different dehydratase (acnD) and an isomerase (prpF) replace the dehydratase prpD; acnD dehydrates (2S,3S)-2-methylcitrate to 2-methyl-trans-aconitate, and prpF isomerizes it to cis-2-methylaconitate. In propanoyl CoA degradation I, propionyl-CoA carboxylase forms (S)-methylmalonyl-CoA, methylmalonyl-CoA epimerase forms (R)-methylmalonyl-CoA, and methylmalonyl-CoA mutase forms succinyl-CoA, which is a central metabolite. (Note that methylmalonyl-CoA mutase requires adenosylcobamide, a form of vitamin B12, for activity.) In propanoyl-CoA degradation II: propionyl-CoA is oxidized to acrylyl-CoA by pco, hydrated to 3-hydroxypropionyl-CoA, hydrolzed to 3-hydroxypropionate, oxidized to 3-oxopropionate (malonate semialdehyde), and oxidized to acetyl-CoA and CO2.
• methylmalonyl-CoA-mutase:
  • mcmA
  • or mcm-large and mcm-small
  • Comment: methylmalonyl-CoA mutase has a catalytic domain and a B12-binding domain. These are usually found in the same protein, which we call mcmA. In Metallosphaera and Pyrococcus, the B12-binding domain is a separate subunit. In Propionibacterium and Methylorubrum, there is an additional subunit with a catalytic domain only; this may have a protective role (PMID:14734568) and is not described here. There's also a mcm-interacting GTPase (known as MeaB or YgfD) that loads B12 onto mcm and protects it from inactivation (see PMC4631608); this is not described here. Some fused mcm proteins include a MeaB domain as well (i.e., Q8F222, Q8Y2U5).
• propionyl-CoA-carboxylase:
  • pccA and pccB
  • or pccA1, pccA2 and pccB
  • Comment: propionyl-CoA carboxylase is a heteromer, usually with alpha and beta subunits pccAB. Haloferax mediterranei has a third subunit as well (pccX), which is not described here. Acidianus brierleyi has a diverged pccA split into two pieces.
• threonine-transport:
  • braC, braD, braE, braF and braG
  • or tdcC
  • or sstT
  • or serP1
  • or phtA
  • or snatA
  • or RR42_RS28305
  • Comment: Transporters were identified using query: transporter:threonine:L-threonine:thr

70 steps (46 with candidates)

Or see definitions of steps

Step	Description	Best candidate	2nd candidate
snatA	L-threonine transporter snatA	CRO22_RS16965	CRO22_RS05425
ltaE	L-threonine aldolase	CRO22_RS08440	CRO22_RS05980
adh	acetaldehyde dehydrogenase (not acylating)	CRO22_RS10475	CRO22_RS05135
ackA	acetate kinase	CRO22_RS11210	CRO22_RS08130
pta	phosphate acetyltransferase	CRO22_RS11250	CRO22_RS13415
gcvP	glycine cleavage system, P component (glycine decarboxylase)	CRO22_RS08180
gcvT	glycine cleavage system, T component (tetrahydrofolate aminomethyltransferase)	CRO22_RS08190	CRO22_RS14440
gcvH	glycine cleavage system, H component (lipoyl protein)	CRO22_RS08185	CRO22_RS06920
lpd	dihydrolipoyl dehydrogenase	CRO22_RS14325	CRO22_RS01860
Alternative steps:
acn	(2R,3S)-2-methylcitrate dehydratase	CRO22_RS05390
acnD	2-methylcitrate dehydratase (2-methyl-trans-aconitate forming)	CRO22_RS05390
acs	acetyl-CoA synthetase, AMP-forming	CRO22_RS01345	CRO22_RS06000
ald-dh-CoA	acetaldehyde dehydrogenase, acylating	CRO22_RS11275
aldA	lactaldehyde dehydrogenase	CRO22_RS10475	CRO22_RS11970
braC	L-alanine/L-serine/L-threonine ABC transporter, substrate binding protein (BraC/NatB)	CRO22_RS12830
braD	L-alanine/L-serine/L-threonine ABC transporter, permease component 1 (BraD/NatD)	CRO22_RS12845	CRO22_RS11435
braE	L-alanine/L-serine/L-threonine ABC transporter, permease component 2 (BraE/NatC)	CRO22_RS13790
braF	L-alanine/L-serine/L-threonine ABC transporter, ATP-binding component 1 (BraF/NatA)	CRO22_RS12835	CRO22_RS11425
braG	L-alanine/L-serine/L-threonine ABC transporter, ATP-binding component 2 (BraG/NatE)	CRO22_RS12840	CRO22_RS11420
D-LDH	D-lactate dehydrogenase	CRO22_RS13410	CRO22_RS11570
dddA	3-hydroxypropionate dehydrogenase	CRO22_RS15360	CRO22_RS11965
DVU3032	L-lactate dehydrogenase, LutC-like component
DVU3033	L-lactate dehydrogenase, fused LutA/LutB components
epi	methylmalonyl-CoA epimerase	CRO22_RS01595
glcD	D-lactate dehydrogenase, FAD-linked subunit 1 (GlcD)	CRO22_RS08580	CRO22_RS13410
glcE	D-lactate dehydrogenase, FAD-linked subunit 2 (GlcE)	CRO22_RS08575
glcF	D-lactate dehydrogenase, FeS subunit GlcF	CRO22_RS08570
gloA*	glyoxylase I	CRO22_RS15080 with CRO22_RS11220
gloB	hydroxyacylglutathione hydrolase (glyoxalase II)	CRO22_RS05560	CRO22_RS07255
grdA	glycine reductase component A1
grdB	glycine reductase component B, gamma subunit
grdC	glycine reductase component C, beta subunit
grdD	glycine reductase component C, alpha subunit
grdE	glycine reductase component B, precursor to alpha/beta subunits
hpcD	3-hydroxypropionyl-CoA dehydratase	CRO22_RS09335	CRO22_RS02520
iolA	malonate semialdehyde dehydrogenase (CoA-acylating)	CRO22_RS10870	CRO22_RS11970
kbl	glycine C-acetyltransferase (2-amino-3-ketobutyrate CoA-ligase)	CRO22_RS04625
L-LDH	L-lactate dehydrogenase	CRO22_RS00655	CRO22_RS13485
lctB	electron-transfer flavoprotein for D-lactate dehydrogenase (NAD+, ferredoxin), small subunit
lctC	electron-transfer flavoprotein for D-lactate dehydrogenase (NAD+, ferredoxin), large subunit	CRO22_RS03420
lctD	D-lactate dehydrogenase (NAD+, ferredoxin), lactate dehydrogenase component	CRO22_RS08580	CRO22_RS13410
lctO	L-lactate oxidase or 2-monooxygenase	CRO22_RS00655
lldE	L-lactate dehydrogenase, LldE subunit
lldF	L-lactate dehydrogenase, LldF subunit
lldG	L-lactate dehydrogenase, LldG subunit
lutA	L-lactate dehydrogenase, LutA subunit
lutB	L-lactate dehydrogenase, LutB subunit
lutC	L-lactate dehydrogenase, LutC subunit
mcm-large	methylmalonyl-CoA mutase, large (catalytic) subunit	CRO22_RS11910	CRO22_RS02165
mcm-small	methylmalonyl-CoA mutase, small (adenosylcobamide-binding) subunit	CRO22_RS11910	CRO22_RS02165
mcmA	methylmalonyl-CoA mutase, fused catalytic and adenosylcobamide-binding components	CRO22_RS11910	CRO22_RS02165
pccA	propionyl-CoA carboxylase, alpha subunit	CRO22_RS11915	CRO22_RS11795
pccA1	propionyl-CoA carboxylase, biotin carboxyl carrier subunit	CRO22_RS11915	CRO22_RS01180
pccA2	propionyl-CoA carboxylase, biotin carboxylase subunit
pccB	propionyl-CoA carboxylase, beta subunit	CRO22_RS11940	CRO22_RS11800
pco	propanyl-CoA oxidase	CRO22_RS09210	CRO22_RS11805
phtA	L-threonine uptake permease PhtA
prpB	2-methylisocitrate lyase
prpC	2-methylcitrate synthase	CRO22_RS14305
prpD	2-methylcitrate dehydratase
prpF	methylaconitate isomerase
RR42_RS28305	L-threonine:H+ symporter
serP1	L-threonine uptake transporter SerP1
sstT	L-threonine:Na+ symporter SstT
tdcB	L-threonine dehydratase	CRO22_RS04015
tdcC	L-threonine:H+ symporter TdcC
tdcE	2-ketobutyrate formate-lyase	CRO22_RS00295
tdh	L-threonine 3-dehydrogenase	CRO22_RS00095	CRO22_RS11230
tynA	aminoacetone oxidase
yvgN	methylglyoxal reductase (NADPH-dependent)	CRO22_RS09775

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.