Methylglyoxal pathway

Propanediol. In its racemic form, 1,2-propanediol is a petroleum-based high-volume chemical with an aimual production of over 500,0001, mostly used to manufacture the unsaturated polyester resins, yet also featuring excellent antifreeze properties. Enantiomerically pure (/ )-1,2-propanediol accumulates along two different pathways via DAHP (3-deoxy-D-flrahmo-heptulosonic acid 7-phosphate) and methylglyoxal, which then is reduced with either... 

Acetone, in the small amounts normally present in the body, is metabolized by hydroxylation to acetol (Eq. 17-7, step a), hydroxylation and dehydration to methylglyoxal (step b), and conversion to D-lactate and pyruvate. A second pathway via 1,2-propanediol and L-lactate is also shown in Eq. 17-7. During fasting the acetone content of human blood may rise to as much as 1.6 mM. As much as two-thirds of this may be converted to glucose.65-69 Accumulation of acetone... 

Du, J., Cai, S., Suzuki, H., Akhand, A.A., Ma, X., Takagi, Y., Miyata, T., Nakashima, I., and Nagase, F. 2003. Involvement of MEKKl/ERK/P21Wafl/Cipl signal transduction pathway in inhibition of IGF-I-mediated cell growth response by methylglyoxal. J Cell Biochem 88 1235-1246. 

Figure 6.19 (d) Pathways for formation of methylglyoxal and glyceraldehyde and possible pathway for reaction 6. (e) Pathways for reactions 5 and 8 (formation of formic and acetic acid). 

This mechanism is appropriate for the addition of S(IV) to formaldehyde, benzaldehyde, methylglyoxal, and hydroxyacetaldehyde, where Eqs. 73-74 represent the acid-catalyzed pathway. The corresponding three-term rate expression is... 

These compounds, exemplified by acrolein, crotonaldehyde, and methyl vinyl ketone, are known to react with ozone and with OH radicals. Photolysis and N03 radical reaction are of minor importance. Under atmospheric conditions the 03 reactions are also of minor significance (Atkinson and Carter, 1984), leaving the OH radical reaction as the major loss process. For the aldehydes, OH radical reaction can proceed via two reaction pathways OH radical addition to the double bond and H-atom abstraction from the -CHO group (Atkinson, 1989). For crotonaldehyde, for example, the OH reaction mechanism is given in Fig. 3. As can be noted from Fig. 3, these a,/3-unsaturated aldehydes are expected to ultimately give rise to a-dicarbonyls such as glyoxal and methylglyoxal. For the a,/3-unsaturated ketones such as methyl vinyl ketone, the major... 

Schulz et al. [234] used dehydro-Shinoda-ascorbic acid, which is the first characteristic intermediate of L-ascorbic acid degradation via the oxidative route, as a starting material of the reaction to distinguish it from the nonoxidative pathway. They found that dehydro-L-ascorbic acid yielded five a-dicarbonyl compounds, namely glyoxal, methylglyoxal, diacetyl, L-threosone, and 3-deoxy-L-threosone (Figure 11.16). They concluded that these a-dicarbonyl compounds are formed from L-ascorbic acid on the oxidative pathway. But, they pointed out that these products can also be produced via the nonoxidative route. They also found that 3-deoxy-L-pentosone is exclusively formed via the nonoxidative route. 

Other compounds have also been produced. For example, hydrogen was produced by a fermentative strategy using hydrogenase (Hyd) and fhl enzymes [199]. 1,2-PDO has also been produced from glycerol in E. coli by a pathway through DHAP and methylglyoxal [200]. Ethanol and other fermentative products have also been produced [201]. Limonene has been produced by an E. coli strain from... 

Condensed-phase SOA formation water-soluble VOCs may dissolve into the aqueous phase of cloud droplets or wet aerosols. Subsequent aqueous-phase reactions (e.g., oxidation and/or oligomerization) can lead to the formation of low-volatility secondary organic material [82-87]. In particular, the dicarbonyl VOCs glyoxal and methylglyoxal have been studied as potential precursors for this SOA formation pathway. Recently, aqueous-phase reactions of isoprene-derived epoxydiols have also been shown to be efficient pathways to SOA formation in the aerosol aqueous phase [88-91]. 

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