Development of isopentenyl phosphate kinases and their application in terpenoid biosynthesis

Ternary complexes of isopentenyl phosphate kinase from Thermococcus paralvinellae reveal molecular determinants of non-natural substrate specificity

Isopentenyl phosphate kinases (IPKs) have recently garnered attention for their central role in biocatalytic "isoprenol pathways," which seek to reduce the synthesis of the isoprenoid precursors to two enzymatic steps. Furthermore, the natural promiscuity of IPKs toward non-natural alkyl-monophosphates (alkyl-Ps) as substrates has hinted at the isoprenol pathways' potential to access novel isoprenoids with potentially useful activities. However, only a handful of IPK crystal structures have been solved to date, and even fewer of these contain non-natural substrates bound in the active site. The current study sought to elucidate additional ternary complexes bound to non-natural substrates using the IPK homolog from Thermococcus paralvinellae (TcpIPK). Four such structures were solved, each bound to a different non-natural alkyl-P and the phosphoryl donor substrate/product adenosine triphosphate (ATP)/adenosine diphosphate (ADP). As expected, the quaternary, tertiary, and secondary structures of TcpIPK closely resembled those of IPKs published previously, and kinetic analysis of a novel alkyl-P substrate highlighted the potentially dramatic effects of altering the core scaffold of the natural substrate. Even more interesting, though, was the discovery of a trend correlating the position of two α helices in the active site with the magnitude of an IPK homolog's reaction rate for the natural reaction. Overall, the current structures of TcpIPK highlight the importance of continued structural analysis of the IPKs to better understand and optimize their activity with both natural and non-natural substrates.

Diosgenin biosynthesis investigation in medicinal herb (Tribulus terrestris) by transcriptome analysis

Next-generation sequencing (NGS) has revolutionized the analysis of specific genes, pathways, and their regulation in various species. Tribulus terrestris L., an annual medicinal herb of Zygophyllaceae family, has gained significant attention due to its diverse medicinal properties, including anti-inflammatory, antimicrobial, and anti-cancer effects. Diosgenin, a steroidal saponin, is the major bioactive compound responsible for the medicinal importance of T. terrestris. However, there is a paucity of information regarding the genes involved in the diosgenin biosynthetic pathway in T. terrestris. To address this gap, this study aimed to identify candidate genes associated with diosgenin biosynthesis through whole transcriptome profiling. A total of ∼7.9 GB of data, comprising 482 million reads, was obtained and assembled into 148,871 unigenes. Subsequently, functional annotations were assigned to 50 % of the unigenes using sequence similarity searches against the NCBI non-redundant (NR), Uniprot, KEGG, Pfam, GO, and COG databases, primarily based on Gene Ontology and KEGG-KAAS pathways. The majority of unigenes associated with the biosynthesis of the steroidal diosgenin backbone exhibited up-regulation in the fruit, leaf, and root tissues, except the SQE gene in root. The differential expression of selected genes was further validated through quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the study identified 21,026 unigenes related to transcription factors and 15,551 unigenes containing simple sequence repeats (SSR). Notably, di-nucleotide SSR motifs exhibited a high repeat frequency. These findings greatly enhance our understanding of the diosgenin biosynthesis pathway and provide a basis for future research in molecular investigation and metabolic engineering, specifically for boosting diosgenin content.

Research Progress in Heterologous Crocin Production

Crocin is one of the most valuable components of the Chinese medicinal plant Crocus sativus and is widely used in the food, cosmetics, and pharmaceutical industries. Traditional planting of C. sativus is unable to fulfill the increasing demand for crocin in the global market, however, such that researchers have turned their attention to the heterologous production of crocin in a variety of hosts. At present, there are reports of successful heterologous production of crocin in Escherichia coli, Saccharomyces cerevisiae, microalgae, and plants that do not naturally produce crocin. Of these, the microalga Dunaliella salina, which produces high levels of β-carotene, the substrate for crocin biosynthesis, is worthy of attention. This article describes the biosynthesis of crocin, compares the features of each heterologous host, and clarifies the requirements for efficient production of crocin in microalgae.