Fungal unspecific peroxygenases (UPOs) are biocatalysts of outstanding interest. Providing access to novel UPOs using a modular secretion system was the central goal of this work. UPOs represent an enzyme class, catalysing versatile oxyfunctionalisation reactions on a broad substrate scope. They are occurring as secreted, glycosylated proteins bearing a haem-thiolate active site and solely rely on hydrogen peroxide as the oxygen source. Fungal peroxygenases are widespread throughout the fungal kingdom and hence a huge variety of UPO gene sequences is available. However, the heterologous production of UPOs in a fast-growing organism suitable for high throughput screening has only succeeded once—enabled by an intensive directed evolution campaign. Here, we developed and applied a modular Golden Gate-based secretion system, allowing the first yeast production of four active UPOs, their one-step purification and application in an enantioselective conversion on a preparative scale. The Golden Gate setup was designed to be broadly applicable and consists of the three module types: i) a signal peptide panel guiding secretion, ii) UPO genes, and iii) protein tags for purification and split-GFP detection. We show that optimal signal peptides could be selected for successful UPO secretion by combinatorial testing of 17 signal peptides for each UPO gene. The modular episomal system is suitable for use in Saccharomyces cerevisiae and was transferred to episomal and chromosomally integrated expression cassettes in Pichia pastoris. Shake flask productions in Pichia pastoris yielded up to 24 mg/L secreted UPO enzyme, which was employed for the preparative scale conversion of a phenethylamine derivative reaching 98.6 % ee. Our results demonstrate a rapid workflow from putative UPO gene to preparative scale enantioselective biotransformations.

Conjugate vaccines against encapsulated pathogens like Streptococcus pneumoniae face many challenges, including the existence of multiple serotypes with a diverse global distribution that constantly requires new formulations and higher coverage. Multivalency is usually achieved by combining capsular polysaccharide–protein conjugates from invasive serotypes, and for S. pneumoniae, this has evolved from 7- up to 20-valent vaccines. These glycoconjugate formulations often contain high concentrations of carrier proteins, which may negatively affect glycoconjugate immune response. This work broadens the scope of an efficient multicomponent strategy, leading to multivalent pneumococcal glycoconjugates assembled in a single synthetic operation. The bioconjugation method, based on the Ugi four-component reaction, enables the one-pot incorporation of two different polysaccharide antigens to a tetanus toxoid carrier, thus representing the fastest approach to achieve multivalency. The reported glycoconjugates incorporate three combinations of capsular polysaccharides 1, 6B, 14, and 18C from S. pneumoniae. The glycoconjugates were able to elicit functional specific antibodies against pneumococcal strains comparable to those shown by mixtures of the two monovalent glycoconjugates.

Systemic acquired resistance (SAR) prepares infected plants for faster and stronger defense activation upon subsequent attacks. SAR requires an information relay from primary infection to distal tissue and the initiation and maintenance of a self‐maintaining phytohormone salicylic acid (SA)‐defense loop.In spatial and temporal resolution, we show that calcium‐dependent protein kinase CPK5 contributes to immunity and SAR. In local basal resistance, CPK5 functions upstream of SA synthesis, perception, and signaling. In systemic tissue, CPK5 signaling leads to accumulation of SAR‐inducing metabolite N‐hydroxy‐L‐pipecolic acid (NHP) and SAR marker genes, including Systemic Acquired Resistance Deficient 1 (SARD1)Plants of increased CPK5, but not CPK6, signaling display an ‘enhanced SAR’ phenotype towards a secondary bacterial infection. In the sard1‐1 background, CPK5‐mediated basal resistance is still mounted, but NHP concentration is reduced and enhanced SAR is lost.The biochemical analysis estimated CPK5 half maximal kinase activity for calcium, K50 [Ca2+], to be c. 100 nM, close to the cytoplasmic resting level. This low threshold uniquely qualifies CPK5 to decode subtle changes in calcium, a prerequisite to signal relay and onset and maintenance of priming at later time points in distal tissue. Our data explain why CPK5 functions as a hub in basal and systemic plant immunity.

The property of the isonitrile group to enable the simultaneous α-addition of a strong electrophile and a nucleophile has always attracted the attention of organic chemists. Its versatility is augmented when recognizing that its high structural compactness, the inertia to most of the naturally occurring functional groups, and relatively prolonged physiological and metabolical stability, convert it into the smallest bioorthogonal group. The discovery and optimization of the isonitrile-tetrazine [4+1] cycloaddition as an alternative tool for the development of ligation and decaging strategies and the recently reported reaction of isonitriles with chlorooximes bring new opportunities for the utilization of this functional group in biological systems. Although several approaches have been reported for the synthesis of isonitrile-modified carbohydrates and polysaccharides, its incorporation in proteins has been barely explored. Besides compiling the reported methods for the assembly of isonitrile-modified proteins, this Mini-Review aims at calling attention to the real potential of this modification for protein ligation, decaging, immobilization, imaging, and many other applications at a low structural and functional cost.

Black pepper (Piper nigrum L.) is known for the high content of piperine, a cinnamoyl amide derivative regarded as largely responsible for the pungent taste of this widely used spice. Despite its long history and worldwide use, the biosynthesis of piperine and related amides has been enigmatic up to now. In this report we describe a specific piperic acid CoA ligase from immature green fruits of P. nigrum. The corresponding enzyme was cloned and functionally expressed in E. coli. The recombinant enzyme displays a high specificity for piperic acid and does not accept the structurally related feruperic acid characterized by a similar C‐2 extension of the general C6‐C3 phenylpropanoid structure. The enzyme is also inactive with the standard set of hydroxycinnamic acids tested including caffeic acid, 4‐coumaric acid, ferulic acid, and sinapic acid. Substrate specificity is corroborated by in silico modeling which suggests a perfect fit of the substrate piperic acid to the active site of the piperic acid CoA ligase. The CoA ligase gene shows highest expression levels in immature green fruits, is also expressed in leaves and flowers, but not in roots. Virus‐induced gene silencing provided some preliminary indications that the production of piperoyl‐CoA is required for the biosynthesis of piperine in black pepper fruits.