Adding α-Ketoglutarate to Semi-hard Cheese Curd Highly Enhances the Conversion of Amino acids to Aroma Compounds

Yvon, Mireille; Berthelot, S.; Gripon, J.C.

doi:10.1016/s0958-6946(99)00011-4

Cited by 154 publications

(149 citation statements)

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“…The soluble metabolites were then analyzed by reverse-phase high-pressure liquid chromatography and ion exclusion high-pressure liquid chromatography with both UV and radioactivity detection, as described previously (65). Metabolites were identified by comparing the retention times with those of appropriate standard compounds, obtained from Sigma.…”

Section: Methodsmentioning

confidence: 99%

“…ldhB is a silent gene that can be activated in ldhdeficient strains via an IS981 element-specific insertion to produce a functional LDH (10). However L. lactis produces 2-hydroxyacids from the 2-keto acids derived from amino acids not only in vitro, using resting cells, but also in cheese (65,66). In L. lactis, the catabolism of the aromatic and branched-chain amino acids that are precursors of aroma compounds is initiated by aminotransferases, producing 2-keto acids.…”

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confidence: 99%

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The d -2-Hydroxyacid Dehydrogenase Incorrectly Annotated PanE Is the Sole Reduction System for Branched-Chain 2-Keto Acids in Lactococcus lactis

et al. 2009

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Hydroxyacid dehydrogenases of lactic acid bacteria, which catalyze the stereospecific reduction of branchedchain 2-keto acids to 2-hydroxyacids, are of interest in a variety of fields, including cheese flavor formation via amino acid catabolism. In this study, we used both targeted and random mutagenesis to identify the genes responsible for the reduction of 2-keto acids derived from amino acids in Lactococcus lactis. The gene panE, whose inactivation suppressed hydroxyisocaproate dehydrogenase activity, was cloned and overexpressed in Escherichia coli, and the recombinant His-tagged fusion protein was purified and characterized. The gene annotated panE was the sole gene responsible for the reduction of the 2-keto acids derived from leucine, isoleucine, and valine, while ldh, encoding L-lactate dehydrogenase, was responsible for the reduction of the 2-keto acids derived from phenylalanine and methionine. The kinetic parameters of the His-tagged PanE showed the highest catalytic efficiencies with 2-ketoisocaproate, 2-ketomethylvalerate, 2-ketoisovalerate, and benzoylformate (V max /K m ratios of 6,640, 4,180, 3,300, and 2,050 U/mg/mM, respectively), with NADH as the exclusive coenzyme. For the reverse reaction, the enzyme accepted D-2-hydroxyacids but not L-2-hydroxyacids. Although PanE showed the highest degrees of identity to putative NADP-dependent 2-ketopantoate reductases (KPRs), it did not exhibit KPR activity. Sequence homology analysis revealed that, together with the Dmandelate dehydrogenase of Enterococcus faecium and probably other putative KPRs, PanE belongs to a new family of D-2-hydroxyacid dehydrogenases which is unrelated to the well-described D-2-hydroxyisocaproate dehydrogenase family. Its probable physiological role is to regenerate the NAD ؉ necessary to catabolize branched-chain amino acids, leading to the production of ATP and aroma compounds.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

The d -2-Hydroxyacid Dehydrogenase Incorrectly Annotated PanE Is the Sole Reduction System for Branched-Chain 2-Keto Acids in Lactococcus lactis

et al. 2009

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“…Knocking out the amino acid anabolism on top of the transaminases still led to minor amounts of 3-methyl butanal and isoamyl alcohol, indicating that an additional pathway or source for α-keto isocaproic acid was also present (Eden et al 2001). Yvon et al (1999) were the first to show that adding α-keto glutarate to cheese curd leads to increased flavour levels due to increased transamination capacity. Later, this was also shown for other cheese types and for sausages (Larrouture et al 2000;Banks et al 2001;Ur-Rehman and Fox 2002;Beck et al 2004;Herranz et al 2004;Tjener et al 2004a;Williams et al 2004).…”

Section: Amino Acid Pool (Reactions 1 and 2)mentioning

confidence: 99%

Branched chain aldehydes: production and breakdown pathways and relevance for flavour in foods

Smit¹,

Engels

Smit

2009

Appl Microbiol Biotechnol

244

173

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Branched aldehydes, such as 2-methyl propanal and 2-and 3-methyl butanal, are important flavour compounds in many food products, both fermented and non-fermented (heat-treated) products. The production and degradation of these aldehydes from amino acids is described and reviewed extensively in literature. This paper reviews aspects influencing the formation of these aldehydes at the level of metabolic conversions, microbial and food composition. Special emphasis was on 3-methyl butanal and its presence in various food products. Knowledge gained about the generation pathways of these flavour compounds is essential for being able to control the formation of desired levels of these aldehydes.

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“…A lack of the substrate KICA was most probably the reason for the absence of high 3-methylbutanal levels. The formation of KICA by transamination has previously been shown to be suboptimal for the production of Leu-derived flavor compounds under cheese ripening conditions (7,42). A combination of transaminase stimulation and the decarboxylase overexpression mutant might result in a major increase in 3-methylbutanal formation and also in higher levels of 2-methylpropanal and 2-methylbutanal, which are derived from valine and isoleucine, respectively.…”

Section: Isobutanoic Acidmentioning

confidence: 99%

Identification, Cloning, and Characterization of a Lactococcus lactis Branched-Chain α-Keto Acid Decarboxylase Involved in Flavor Formation

Smit

Vlieg

Engels

et al. 2005

Appl Environ Microbiol

122

139

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The biochemical pathway for formation of branched-chain aldehydes, which are important flavor compounds derived from proteins in fermented dairy products, consists of a protease, peptidases, a transaminase, and a branched-chain ␣-keto acid decarboxylase (KdcA). The activity of the latter enzyme has been found only in a limited number of Lactococcus lactis strains. By using a random mutagenesis approach, the gene encoding KdcA in L. lactis B1157 was identified. The gene for this enzyme is highly homologous to the gene annotated ipd, which encodes a putative indole pyruvate decarboxylase, in L. lactis IL1403. Strain IL1403 does not produce KdcA, which could be explained by a 270-nucleotide deletion at the 3 terminus of the ipd gene encoding a truncated nonfunctional decarboxylase. The kdcA gene was overexpressed in L. lactis for further characterization of the decarboxylase enzyme. Of all of the potential substrates tested, the highest activity was observed with branchedchain ␣-keto acids. Moreover, the enzyme activity was hardly affected by high salinity, and optimal activity was found at pH 6.3, indicating that the enzyme might be active under cheese ripening conditions.Flavor formation in cheeses is mainly the result of catabolism of milk proteins, sugar, and lipids. Degradation of proteins into amino acids followed by conversion of these amino acids by Lactococcus spp. is very important for flavor formation in semihard types of cheese, like Gouda (for reviews see references 12, 25, 38, and 43). One of the predominant amino acid conversion routes is initiated by transaminases. Transamination of amino acids yields the corresponding ␣-keto acids, which do not have strong flavor properties (12, 13) but are the precursors of various aldehydes, alcohols, acids, and (thio-)esters. The latter compounds generally have much lower odor thresholds and strongly contribute to cheese flavor. This is exemplified by the production of flavor compounds from leucine. Transamination of leucine results in the production of ␣-isocaproic acid (KICA). Interestingly, only a limited number of Lactococcus lactis strains are capable of decarboxylating this ␣-keto acid to 3-methylbutanal (36, 37). The decarboxylating activity is observed mainly in L. lactis strains with nondairy origins, whereas the industrial strains tested hardly showed this activity (36). Subsequently, (de)hydrogenation of 3-methylbutanal results in 3-methylbutanol or 3-methylbutyric acid, which also contributes to the flavor of cheese, but the odor thresholds for these compounds are higher than the odor threshold for 3-methylbutanal (24, 29). The rate-determining step in this route is the decarboxylation of KICA, and therefore, control of this enzyme offers good prospects for the design of starter cultures with tailored flavor production (37, 43).The enzyme performing this reaction has not been identified. A number of thiamine pyrophosphate (TPP)-dependent

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Adding α-Ketoglutarate to Semi-hard Cheese Curd Highly Enhances the Conversion of Amino acids to Aroma Compounds

Cited by 154 publications

References 0 publications

The d -2-Hydroxyacid Dehydrogenase Incorrectly Annotated PanE Is the Sole Reduction System for Branched-Chain 2-Keto Acids in Lactococcus lactis

The d -2-Hydroxyacid Dehydrogenase Incorrectly Annotated PanE Is the Sole Reduction System for Branched-Chain 2-Keto Acids in Lactococcus lactis

Branched chain aldehydes: production and breakdown pathways and relevance for flavour in foods

Identification, Cloning, and Characterization of a Lactococcus lactis Branched-Chain α-Keto Acid Decarboxylase Involved in Flavor Formation

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