Oral enzymatic detoxification system: Insights obtained from proteome analysis to understand its potential impact on aroma metabolization

Abstract

The oral cavity is an entry path into the body, enabling the intake of nutrients but also leading to the ingestion of harmful substances. Thus, saliva and oral tissues contain enzyme systems that enable the early neutralization of xenobiotics as soon as they enter the body. Based on recently published oral proteomic data from several research groups, this review identifies and compiles the primary detoxification enzymes (also known as xenobiotic-metabolizing enzymes) present in saliva and the oral epithelium. The functions and the metabolic activity of these enzymes are presented. Then, the activity of these enzymes in saliva, which is an extracellular fluid, is discussed with regard to the salivary parameters. The next part of the review presents research evidencing oral metabolization of aroma compounds and the putative involved enzymes. The last part discusses the potential role of these enzymatic reactions on the perception of aroma compounds in light of recent pieces of evidence of in vivo oral metabolization of aroma compounds affecting their release in mouth and their perception. Thus, this review highlights different enzymes appearing as relevant to explain aroma metabolism in the oral cavity. It also points out that further works are needed to unravel the effect of the oral enzymatic detoxification system on the perception of food flavor in the context of the consumption of complex food matrices, while considering the impact of food oral processing. Thus, it constitutes a basis to explore these biochemical mechanisms and their impact on flavor perception.

Metabolism of Cysteine Conjugates and Production of Flavor Sulfur Compounds by a Carbon–Sulfur Lyase from the Oral Anaerobe Fusobacterium nucleatum

“…Additionally, two other putative metabolites were identified, namely diallyl sulfide ( m / z 114, RT: 9.61 min, RI exp : 1154RI lit : 1148) and diallyl disulfide ( m / z 146, RT: 20.49 min, RI exp : 1493RI lit : 1475). Since analysis of the allyl thiol standard led to the identification of low amounts of these two compounds, these are probably formed following nonenzymatic oxidation and/or alkylation of allyl thiol or result from the reaction with other enzymes present in saliva, as previously observed for similar sulfur compounds. , Salivary C–S lyase activity was previously suggested to come from PLP-dependent enzymes. , Hence, the same assay supplemented with 100 μM PLP cofactor was performed. This assay led to a slightly but significantly enhanced production of thiols (Figure A,B), thus suggesting that the assessed C–S lyases are PLP cofactor-dependent.…”

“…The oral metabolism of flavor compounds is a new field of food research that has emerged recently, with studies pointing out the importance of the perception of flavor molecules metabolized in the oral cavity. Indeed, some flavor compounds entering the oral cavity are rapidly metabolized by saliva and the oral mucosa, which not only leads to a decrease in flavor compounds but also the generation of newly formed compounds with new sensory properties. , Little is known concerning the related biochemical reactions occurring in the mouth, but some evidence points out the possible involvement of human xenobiotic-metabolizing enzymes , as well as oral microbiota enzymes . Very few studies have investigated the role of the oral microbiota in flavor perception.…”

“…37,38 Salivary C−S lyase activity was previously suggested to come from PLP-dependent enzymes. 3,5 Hence, the same assay supplemented with 100 μM PLP cofactor was performed. This assay led to a slightly but significantly enhanced production of thiols (Figure 2A,B), thus suggesting that the assessed C−S lyases are PLP cofactor-dependent.…”

“…This metabolic activity plays an important role in aroma perception . The metabolism of aroma compounds in the oral cavity originates from the presence of xenobiotic-metabolizing enzymes in saliva and the oral mucosa. , In addition to host enzymes, the oral cavity is colonized by microorganisms, which have their own metabolism and enzymes. A body of evidence suggests that oral microbiota metabolism takes part in in-mouth aroma metabolism through the involvement of specific microbial enzymes. − For instance, glycosidases and carbon–sulfur lyases (C–S lyases) have been suggested to play a role in the metabolism of two classes of aroma precursors, namely glycoside conjugates and cysteine conjugates, respectively .…”

“…2 The metabolism of aroma compounds in the oral cavity originates from the presence of xenobiotic-metabolizing enzymes in saliva and the oral mucosa. 3,4 In addition to host enzymes, the oral cavity is colonized by microorganisms, which have their own metabolism and enzymes. A body of evidence suggests that oral microbiota metabolism takes part in in-mouth aroma metabolism through the involvement of specific microbial enzymes.…”