Elucidating the Sugar Tailoring Steps in the Cytorhodin Biosynthetic Pathway

Anthracycline antitumor cytorhodins X and Y feature a rare 9α-glycoside and 7-dexoy-aglycone. Characterization of the cytorhodin gene cluster from <i>Streptomyces</i> sp. SCSIO 1666 through gene inactivations and metabolite analyses reveals three glycosyltransferases (GTs) involved in the sugar tailoring steps. The duo of CytG1 and CytL effects C-7 glycosylation with l-rhodosamine whereas the iterative GT CytG3 and CytW similarly modifies both C-9 and C-10 positions. CytG2 also acts iteratively by incorporating the second and third sugar moiety into the trisaccharide chains at the C-7 or C-10 position

Additional file 1 of Prognostic potential of liver injury in patients with dilated cardiomyopathy: a retrospective study

Additional file 1: Table S1. Mean dose of drug during hospitalization in the study population. Table S2. Cause of death in the study population. Figure S1. Kaplan–Meier curves of stratified analysis showed the occurrence of the primary outcome in patients with and without liver injury. (A) age ≤ 50 years, (B) age > 50 years, (C) male, (D) female

Discovery of a New Family of Dieckmann Cyclases Essential to Tetramic Acid and Pyridone-Based Natural Products Biosynthesis

Bioinformatic analyses indicate that TrdC, SlgL, LipX₂, KirHI, and FacHI belong to a group of highly homologous proteins involved in biosynthesis of actinomycete-derived tirandamycin B, streptolydigin, α-lipomycin, kirromycin, and factumycin, respectively. However, assignment of their biosynthetic roles has remained elusive. Gene inactivation and complementation, <i>in vitro</i> biochemical assays with synthetic analogues, point mutations, and phylogenetic tree analyses reveal that these proteins represent a new family of Dieckmann cyclases that drive tetramic acid and pyridone scaffold biosynthesis

Biosynthetic Baeyer–Villiger Chemistry Enables Access to Two Anthracene Scaffolds from a Single Gene Cluster in Deep-Sea-Derived <i>Streptomyces olivaceus</i> SCSIO T05

Four known compounds, rishirilide B (<b>1</b>), rishirilide C (<b>2</b>), lupinacidin A (<b>3</b>), and galvaquinone B (<b>4</b>), representing two anthracene scaffolds typical of aromatic polyketides, were isolated from a culture of the deep-sea-derived <i>Streptomyces olivaceus</i> SCSIO T05. From the <i>S. olivaceus</i> producer was cloned and sequenced the <i>rsd</i> biosynthetic gene cluster (BGC) that drives rishirilide biosynthesis. The structural gene <i>rsdK</i>₂ inactivation and heterologous expression of the <i>rsd</i> BGC confirmed the single <i>rsd</i> BGC encodes construction of <b>1</b>–<b>4</b> and, thus, accounts for two anthracene scaffolds. Precursor incubation experiments with ¹³C-labeled acetate revealed that a Baeyer–Villiger-type rearrangement plays a central role in construction of <b>1</b>–<b>4</b>. Two luciferase monooxygenase components, along with a reductase component, are presumably involved in the Baeyer–Villiger-type rearrangement reaction enabling access to the two anthracene scaffold variants. Engineering of the <i>rsd</i> BGC unveiled three SARP family transcriptional regulators, enhancing anthracene production. Inactivation of <i>rsdR</i>₄, a MarR family transcriptional regulator, failed to impact production of <b>1</b>–<b>4</b>, although production of <b>3</b> was slightly improved; most importantly <i>rsdR</i>₄ inactivation led to the new adduct <b>6</b> in high titer. Notably, inactivation of <i>rsdH</i>, a putative amidohydrolase, substantially improved the overall titers of <b>1</b>–<b>4</b> by more than 4-fold

Deciphering the Biosynthetic Origin of l-<i>allo</i>-Isoleucine

The nonproteinogenic amino acid l-<i>allo</i>-isoleucine (l-<i>allo</i>-Ile) is featured in an assortment of life forms comprised of, but not limited to, bacteria, fungi, plants and mammalian systems including <i>Homo sapiens</i>. Despite its ubiquity and functional importance, the specific origins of this unique amino acid have eluded characterization. In this study, we describe the discovery and characterization of two enzyme pairs consisting of a pyridoxal 5′-phosphate (PLP)-linked aminotransferase and an unprecedented isomerase synergistically responsible for the biosynthesis of l-<i>allo</i>-Ile from l-isoleucine (l-Ile) in natural products. DsaD/DsaE from the desotamide biosynthetic pathway in <i>Streptomyces scopuliridis</i> SCSIO ZJ46, and MfnO/MfnH from the marformycin biosynthetic pathway in <i>Streptomyces drozdowiczii</i> SCSIO 10141 drive l-<i>allo</i>-Ile generation in each respective system. In vivo gene inactivations validated the importance of the DsaD/DsaE pair and MfnO/MfnH pair in l-<i>allo</i>-Ile unit biosynthesis. Inactivation of PLP-linked aminotransferases DsaD and MfnO led to significantly diminished desotamide and marformycin titers, respectively. Additionally, inactivation of the isomerase genes <i>dsaE</i> and <i>mfnH</i> completely abolished production of all l-<i>allo</i>-Ile-containing metabolites in both biosynthetic pathways. Notably, in vitro biochemical assays revealed that DsaD/DsaE and MfnO/MfnH each catalyze a bidirectional reaction between l-<i>allo</i>-Ile and l-Ile. Site-directed mutagenesis experiments revealed that the enzymatic reaction involves a PLP-linked ketimine intermediate and uses an arginine residue from the <i>C</i>-terminus of each isomerase to epimerize the amino acid β-position. Consequently, these data provide important new insight into the origins of l-<i>allo</i>-Ile in natural products with medicinal potential and illuminate new possibilities for biotool development

Cytotoxic Anthracycline Metabolites from a Recombinant <i>Streptomyces</i>

The C7 (C9 or C10)-<i>O</i>-l-rhodosamine-bearing anthracycline antibiotic cytorhodins and their biosynthetic intermediates were recently isolated from <i>Streptomyces</i> sp. SCSIO 1666. Cosmid p17C4 from the <i>Streptomyces lydicus</i> genomic library, which harbors both the biosynthetic genes for l-rhodinose (or 2-deoxy-l-fucose) and its glycosyltransferase (encoded by slgG), was introduced into SCSIO 1666 to yield the recombinant strain <i>Streptomyces</i> sp. SCSIO 1666/17C4. Chemical investigations of this strain’s secondary metabolic potential revealed the production of different anthracyclines featuring C7-<i>O</i>-l-rhodinose (or 2-deoxy-l-fucose) instead of the typically observed l-rhodosamine. Purification of the fermentation broth yielded 12 new anthracycline antibiotics including three new ε-rhodomycinone derivatives, <b>1</b>, <b>4</b>, and <b>8</b>, nine new β-rhodomycinone derivatives, <b>2</b>, <b>3</b>, <b>5</b>–<b>7</b>, and <b>9</b>–<b>12</b>, and three known compounds, l-rhodinose-l-rhodinose-l-rhodinose­rhodomycinone (<b>13</b>), ε-rhodomycinone (<b>14</b>), and γ-rhodomycinone (<b>15</b>). All compounds were characterized on the basis of detailed spectroscopic analyses and comparisons with previously reported data. These compounds exhibited cytotoxicity against a panel of human cancer cell lines. Significantly, compounds <b>4</b> and <b>13</b> displayed pronounced activity against HCT-116 as characterized by IC₅₀ values of 0.3 and 0.2 μM, respectively; these IC₅₀ values are comparable to that of the positive control epirubicin