Coenzyme biosynthesis: enzyme mechanism, structure and inhibition

On the evolution of coenzyme biosynthesis

Covering: up to 2022The report provides a broad approach to deciphering the evolution of coenzyme biosynthetic pathways. Here, these various pathways are analyzed with respect to the coenzymes required for this purpose. Coenzymes whose biosynthesis relies on a large number of coenzyme-mediated reactions probably appeared on the scene at a later stage of biological evolution, whereas the biosyntheses of pyridoxal phosphate (PLP) and nicotinamide (NAD⁺) require little additional coenzymatic support and are therefore most likely very ancient biosynthetic pathways.

The coenzyme/protein pair and the molecular evolution of life

Covering: up to 2020What was first? Coenzymes or proteins? These questions are archetypal examples of causal circularity in living systems. Classically, this "chicken-and-egg" problem was discussed for the macromolecules RNA, DNA and proteins. This report focuses on coenzymes and cofactors and discusses the coenzyme/protein pair as another example of causal circularity in life. Reflections on the origin of life and hypotheses on possible prebiotic worlds led to the current notion that RNA was the first macromolecule, long before functional proteins and hence DNA. So these causal circularities of living systems were solved by a time travel into the past. To tackle the "chicken-and-egg" problem of the protein-coenzyme pair, this report addresses this problem by looking for clues (a) in the first hypothetical biotic life forms such as protoviroids and the last unified common ancestor (LUCA) and (b) in considerations and evidence of the possible prebiotic production of amino acids and coenzymes before life arose. According to these considerations, coenzymes and cofactors can be regarded as very old molecular players in the origin and evolution of life, and at least some of them developed independently of α-amino acids, which here are evolutionarily synonymous with proteins. Discussions on "chicken-and-egg" problems open further doors to the understanding of evolution.

Aldehyde catalysis - from simple aldehydes to artificial enzymes

Chemists have been learning and mimicking enzymatic catalysis in various aspects of organic synthesis. One of the major goals is to develop versatile catalysts that inherit the high catalytic efficiency of enzymatic processes, while being effective for a broad scope of substrates. In this field, the study of aldehyde catalysts has achieved significant progress. This review summarizes the application of aldehydes as sustainable and effective catalysts in different reactions. The fields, in which the aldehydes successfully mimic enzymatic systems, include light energy absorption/transfer, intramolecularity introduction through tether formation, metal binding for activation/orientation and substrate activation via aldimine formation. Enantioselective aldehyde catalysis has been achieved with the development of chiral aldehyde catalysts. Direct simplification of aldehyde-dependent enzymes has also been investigated for the synthesis of noncanonical chiral amino acids. Further development in aldehyde catalysis is expected, which might also promote exploration in fields related to prebiotic chemistry, early enzyme evolution, etc.

Identification of mutations restricting autocatalytic activation of bacterial L-aspartate α-decarboxylase

Bacterial L-aspartate α-decarboxylase (PanD) specifically catalyzes the decarboxylation of L-aspartic acid to β-alanine. It is translated as an inactive pro-protein, then processed by self-cleavage to form two small subunits with catalytic activity. There is a significant difference in the efficiency of this process among the reported PanDs, while the structural basis remains unclear. More PanDs with known sequences and characterized properties are needed to shed light on the molecular basis of the self-cleavage process. In this study, PanD genes from 33 selected origins were synthesized and expressed; using purified recombinant enzymes, their self-processing properties were characterized and classified. Three classes of PanDs were acquired based on their self-cleavage efficiency. Combined with the phylogenetic analysis and structure comparison, sited-directed mutagenesis was performed to investigate the effects of four mutants on self-processing. In comparison with the wild-type (96.4%), the self-cleavage efficiencies of mutants V23E, I26C, T27A, and E56S were decreased to 90.5, 83.6, 74.4 and 81.2%, respectively. The results indicated that residues of V23, I26, T27 and E56 were critical to the self-cleavage processing of PanDs. This work provided further understanding to the self-cleavage processing of PanDs, which may contribute to protein engineering of the enzyme.

Detection and Prevention of Aggregation-based False Positives in STD-NMR-based Fragment Screening

Aggregation of small organic compounds is a problem encountered in a variety of assay screening formats where it often results in detection of false positives. A saturation transfer difference-NMR-detected screen of a commercially available fragment library, followed by biochemical assay, identified several inhibitors of the enzyme ketopantoate reductase. These inhibitors were subsequently revealed to be aggregation-based false positives. Modification of the fragment screen by addition of detergent in the saturation transfer difference-NMR experiments allowed an assay format to be developed that resulted in the identification of genuine hit molecules suitable for further development.

Comparative metabolomic analysis of Sinorhizobium sp. C4 during the degradation of phenanthrene

Comparative metabolic responses of Sinorhizobium sp. C4 were investigated. Comprehensive metabolites profiles, including polar metabolites, fatty acids, and polyhydroxyalkanoates were evaluated through untargeted metabolome analyses. Intracellular metabolomes during the degradation of phenanthrene were compared with those from natural carbon sources. Principal component analysis showed a clear separation of metabolomes of phenanthrene degradation from other carbon sources. Shift to more hydrophobic fatty acid was observed from the analysis of fatty acid methyl ester. Polyhydroxyalkanoate from strain C4 was composed mainly with 3-hydroxybutyric acid and small amount of 3-hydroxypentanoic acid, while the monomeric composition was independent on carbon sources. However, the amount of polyhydroxyalkanoates during degradation of phenanthrene was 50–210% less than those from other carbon sources. Among 207 gas chromatography–mass spectrometry peaks from the polar metabolite fraction, 60% of the peaks were identified and compared. Several intermediates in tricarboxylic acid cycles and glycolysis were increased during phenanthrene degradation. Accumulation of trehalose was also evident in the phenanthrene-treated bacterium. Some amino acid, including branched amino acids, glycine, homoserine, and valine, were also increased, while more than 70% of identified metabolites were decreased during the phenanthrene metabolism. Accumulation of sulfur amino acids and nicotinic acid suggested the possible oxidative stress conditions during phenanthrene metabolism.

Elucidating biosynthetic pathways for vitamins and cofactors

The elucidation of the pathways to the water-soluble vitamins and cofactors has provided many biochemical and chemical challenges. This is a reflection both of their complex chemical nature, and the fact that they are often made in small amounts, making detection of the enzyme activities and intermediates difficult. Here we present an orthogonal review of how these challenges have been overcome using a combination of methods, which are often ingenious. We make particular reference to some recent developments in the study of biotin, pantothenate, folate, pyridoxol, cobalamin, thiamine, riboflavin and molybdopterin biosynthesis.