The protein Glycose-6-Phosphate Dehydrogenase is an enzyme involved in the metabolic pathways of the majority of organisms. Leuconostoc mesenteroides is a Bacilli Gram-positive bacterium that expresses this enzyme.
Function
The Glucose-6-Phosphate Dehydrogenase is involved in the processing of carbohydrates as it has important roles in the glucose metabolic process (glycolysis and pentose phosphate pathway).
It also has a role in protecting cells from destruction as it produces the co-factor NADPH which plays a role in protecting cells from reactive oxygen species [1].
Genomic context
It is coded by the G6PD gene (1461 nucleotides)[2].
Catalytic activity
D-glucose 6-phosphate + NAD+ → 6-phospho-D-glucono-1,5-lactone + H+ + NADH[3]
KM=114 µM for G6PD (with NADP), KM=69 µM for G6PD (with NAD),
KM=8.0 µM for NADP, KM=160 µM for NAD.
Its regulation depends on the concentration of substrate and coenzyme, rate limiting step in pentose phosphate pathway[4].
Optimum pH for its activity is 5.4 - 8.9.
Evolutionary conservation
The different structures conserved evolutionary can be observed according to the scale following.
Check, as determined by ConSurfDB.
Mutations
Mutagenesis of this enzyme induces catalytic activity loss: more than 200 mutations have been identified.
A mutation in a nucleotide in the sequence coding for G6PD leads to disruption of the normal expression of the enzyme, or to a disruption in the amino acid structure of the enzyme which leads to a loss or decrease of catalytic activity toward its substrate.
The most common mutations in the amino acids sequence found that induce a loss of catalytic activity are a substitution of the bold amino acids by another one[5]:
MVSEIKTLVT FFGGTGDLAK R'KLYPSVFNL YKKGYLQKHF AIVGTAR'QAL NDDEFKQLVR DSIKDFTDDQ AQAEAFIEHF SYRAHDVTDA ASYAVLKEAI EEAADKFDID GNRIFYMSVA PRFFGTIAKY LKSEGLLADT GYNRLMIEKP FGTSYDTAAE LQNDLENAFD DNQLFRID'H'Y LGKEMVQNIA ALRFGNPIFD AAWNKDYIKN VQVTLSEVLG VEERAGYYDT AGALLDMIQN HTMQIVGWLA MEKPESFTDK DIRAAKNAAF NALKIYDEAE VNKYFVRAQY GAGDSADFKP YLEELDVPAD SKNNTFIAGE LQFDLPRWEG VPFYVRSGKR LAAKQTRVDI VFKAGTFNFG SEQEAQEAVL SIIIDPKGAI ELKLNAKSVE DAFNTRTIDL GWTVSDEDKK NTPEPYERMI HDTMNGDGSN FADWNGVSIA WKFVDAISAV YTADKAPLET YKSGSMGPEA SDKLLAANGD AWVFKG.
This sequence being the normal protein sequence found in L. mesenteroides.
Structural highlights
It is formed of a homodimer, so a dimer of two identical monomers[6]. Each monomer is composed of 2 domains,
Depending on several conditions, it can dimerize to form tetramers. Each monomer in the complex has a substrate binding site that binds to G6P, and a catalytic coenzyme binding site that binds to NADP+/NADPH using the Rossman fold.
This is a sample scene created with SAT to by Group, and another to make of the protein.
