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Encoded in the Saccharomyces cerevisiae (strain ATCC 204508 / S288c) gene CYB2 the protein Flavocytochrome b(2)

It is an Oxidoreductase categorized according to IUB as EC: 1.1.2.3.

Function

Flavocytochrome b(2) (Arg289Lys mutant) from Saccharomyces cerevisiae is an oxidoreductase that couples dehydrogenation of L-lactate to cytochrome c reduction by electron transfer. It is one step of the bacterial lactate metabolic pathway.

Reaction

Similar oxidants that can be used to perform the reaction in vitro are ferricyanide, phenozine methosulfate and quinone (experiment first performed 1963 by Nygaard^[1], later in 1966 described by Symons and Burgoyne]^[2]. The Yeasts L-Lactate Dehydrogenase can be inhibited by heavy metals, oxygen, glycerate, oxalate, malate, phenylpyruvate and fatty acids [Nygaard 1963]^[3]. The Enzyme shows a specificity for L-lactate but none for the D-isomer or -hydroxybutyrate.

Relevance

While the function of cytochrome b2 is to couple L-lactate dehydrogenation to cytochrome c reduction; the mutant ARG289LYS is changing the kinetics of the reactions. It is rising the K_i of several components in comparison to the wild-type, while k_cat and K_M are also changed by a factor of 10. It changes also the induction by L-lactate. R289K-b(2) eing a component of the mitochondrial inter membrane space

Structural highlights

Global Symmetry Cyclic - C4 Global Stoichiometry Homotetramer A4

Flavocytochrome b(2) is a tetrameric enzyme [Jacq and Lederer, 1972]. Each of the four identical subunits is composed by one single polypeptide chain.

Each subunit contains a binding site for the selectively non-covalently binding of the cofactor FM3- (FlavinMonoNucleotide),

multiple image

https://www.wikiwand.com/de/Flavinmononukleotid

as well as one in with the iron complexed in the tetrapyrrole ring interacts with heme b(2-) cofactor [Risler and Groudinsky, 1973].

https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:60344

The amino acid sequence in the heme binding region was first determined by Guidard et al. (1974).

For every subunit the crystallized preparation analysis determined a molecular weight of the chain of 36 kD [Appleby and Morton] and the chain of 21 kD [Jacq and Lederer, 1974].

Arginin 289 to Lysine

http://www.worthington-biochem.com/yldhs/

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