Improved synthesis of 3,4-dihydroxyphenylpyruvic acid

Production of Salvianic Acid A from l-DOPA via Biocatalytic Cascade Reactions

Salvianic acid A (SAA), as the main bioactive component of the traditional Chinese herb Salvia miltiorrhiza, has important application value in the treatment of cardiovascular diseases. In this study, a two-step bioprocess for the preparation of SAA from l-DOPA was developed. In the first step, l-DOPA was transformed to 3,4-dihydroxyphenylalanine (DHPPA) using engineered Escherichia coli cells expressing membrane-bound L-amino acid deaminase from Proteus vulgaris. After that, the unpurified DHPPA was directly converted into SAA by permeabilized recombinant E. coli cells co-expressing d-lactate dehydrogenase from Pediococcus acidilactici and formate dehydrogenase from Mycobacterium vaccae N10. Under optimized conditions, 48.3 mM of SAA could be prepared from 50 mM of l-DOPA, with a yield of 96.6%. Therefore, the bioprocess developed here was not only environmentally friendly, but also exhibited excellent production efficiency and, thus, is promising for industrial SAA production.

Presence of Bromotyrosine Alkaloids in Marine Sponges Is Independent of Metabolomic and Microbiome Architectures

Marine sponge holobionts are prolific sources of natural products. One of the most geographically widespread classes of sponge-derived natural products is the bromotyrosine alkaloids. A distinguishing feature of bromotyrosine alkaloids is that they are present in phylogenetically disparate sponges. In this study, using sponge specimens collected from Guam, the Solomon Islands, the Florida Keys, and Puerto Rico, we queried whether the presence of bromotyrosine alkaloids potentiates metabolomic and microbiome conservation among geographically distant and phylogenetically different marine sponges. A multi-omic characterization of sponge holobionts revealed vastly different metabolomic and microbiome architectures among different bromotyrosine alkaloid-harboring sponges. However, we find statistically significant correlations between the microbiomes and metabolomes, signifying that the microbiome plays an important role in shaping the overall metabolome, even in low-microbial-abundance sponges. Molecules mined from the polar metabolomes of these sponges revealed conservation of biosynthetic logic between bromotyrosine alkaloids and brominated pyrrole-imidazole alkaloids, another class of marine sponge-derived natural products. In light of prior findings postulating the sponge host itself to be the biosynthetic source of bromotyrosine alkaloids, our data now set the stage for investigating the causal relationships that dictate the microbiome-metabolome interconnectedness for marine sponges in which the microbiome may not contribute to natural product biogenesis.IMPORTANCE Our work demonstrates that phylogenetically and geographically distant sponges with very different microbiomes can harbor natural product chemical classes that are united in their core chemical structures and biosynthetic logic. Furthermore, we show that independent of geographical dispersion, natural product chemistry, and microbial abundance, overall sponge metabolomes tightly correlate with their microbiomes.

Structural and functional characterization of 4-hydroxyphenylpyruvate dioxygenase from the thermoacidophilic archaeon Picrophilus torridus

4-Hydroxyphenylpyruvate dioxygenase (Hpd, EC 1.13.11.27) catalyzes the conversion of 4-hydroxyphenylpyruvate into homogentisate in the second step of oxidative tyrosine catabolism. This pathway is known from bacteria and eukaryotes, but so far no archaeal Hpd has been described. Here, we report the biochemical characterization of an Hpd from the extremophilic archaeon Picrophilus torridus (Pt_Hpd), together with its three-dimensional structure at a resolution of 2.6 Å. Two pH optima were observed at 50 °C: pH 4.0 (close to native conditions) and pH 7.0. The enzyme showed only moderate thermostability and was inactivated with a half-life of ~1.5 h even under optimal reaction conditions. At the ideal physiological growth conditions of P. torridus, Pt_Hpd was inactive after 1 h, showing that the enzyme is protected in vivo from denaturation and/or is only partially adapted to the harsh environmental conditions in the cytosol of P. torridus. The influence of different additives on the activity was investigated. Pt_Hpd exhibited a turnover number k(cat) of 9.9 ± 0.6 s(-1) and a substrate binding affinity K(m) of 142 ± 23 µM. In addition, substrate inhibition with a binding affinity K(i) of 1.9 ± 0.3 mM was observed. Pt_Hpd is compared with isoenzymes from other species and the putative bacterial origin of the gene is discussed.

Synthesis of a bromotyrosine-derived natural product inhibitor of mycothiol- S -conjugate amidase

Recently we described the structures of two new bromotyrosine-derived alkaloids that inhibit the detoxification enzyme mycothiol-S-conjugate amidase (MCA) from Mycobacterium tuberculosis. Here we describe a concise total synthesis of bromotyrosine oxime 1. The six-step synthesis of 1 utilized a trifluoromethyloxazole intermediate, whose hydrolysis product underwent alkylation and coupling to agmatine to give the inhibitor in approximately 40% overall yield. Oxime 1 inhibited MCA and its homolog AcGI deacetylase with IC(50) values of 30 and 150 microM, respectively.

Combinatorial synthesis through disulfide exchange: discovery of potent psammaplin A type antibacterial agents active against methicillin-resistant Staphylococcus aureus (MRSA)

Psammaplin A is a symmetrical bromotyrosine-derived disulfide natural product isolated from the Psammaplysilla sponge, which exhibits in vitro antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Inspired by the structure of this marine natural product, a combinatorial scrambling strategy for the construction of heterodimeric disulfide analogues was developed and applied to the construction of a 3828-membered library starting from 88 homodimeric disulfides. These psammaplin A analogues were screened directly against various gram positive bacterial strains leading to the discovery of a series of potent antibacterial agents active against methicillin-resistant Staphylococcus aureus (MRSA). Among the most active leads derived from these studies are compounds 104, 105, 113, 115, 123, and 128. The present, catalytically-induced, disulfide exchange strategy may be extendable to other types of building blocks bearing thiol groups facilitating the construction of diverse discovery-oriented combinatorial libraries.