The cyclic depsipeptide skyllamycin A is a potent inhibitor of the platelet-derived growth factor (PDGF) signaling pathway by inhibiting binding of homodimeric PDGF BB to the PDGF β-receptor. Its structure contains a cinnamoyl side chain and shows a high amount of β-hydroxylated amino acids as well as an unusual α-hydroxyglycine moiety as a rare structural modification. The skyllamycin biosynthetic gene cluster was cloned and sequenced from Streptomyces sp. Acta 2897. Its analysis revealed the presence of open reading frames encoding proteins for fatty acid precursor biosynthesis, non-ribosomal peptide synthetases, regulators, and transporters along with other modifying enzymes. Specific in-frame mutagenesis of these tailoring enzymes resulted in the production of novel skyllamycin derivatives revealing that β-hydroxy groups in skyllamycin A are introduced by a promiscuous cytochrome P450 monooxygenase, whereas a two-component flavin-dependent monooxygenase is involved in α-hydroxylation.
Chiral amines are valuable building blocks for the pharmaceutical industry. ω-TAms have emerged as an exciting option for their synthesis, offering a potential "green alternative" to overcome the drawbacks associated with conventional chemical methods. In this review, we explore the application of ω-TAms for pharmaceutical production. We discuss the diverse array of reactions available involving ω-TAms and process considerations of their use in both kinetic resolution and asymmetric synthesis. With the aid of specific drug intermediates and APIs, we chart the development of ω-TAms using protein engineering and their contribution to elegant one-pot cascades with other enzymes, including carbonyl reductases (CREDs), hydrolases and monoamine oxidases (MAOs), providing a comprehensive overview of their uses, beginning with initial applications through to the present day.
Amine
transaminases offer an environmentally sustainable synthesis
route for the production of pure chiral amines. However, their catalytic
efficiency toward bulky ketone substrates is greatly limited by steric
hindrance and therefore presents a great challenge for industrial
synthetic applications. We hereby report an example of rational transaminase
enzyme design to help alleviate these challenges. Starting from the Vibrio fluvialis amine transaminase that has no detectable
catalytic activity toward the bulky aromatic ketone 2-acetylbiphenyl,
we employed a rational design strategy combining in silico and in vitro studies to engineer the transaminase
enzyme with a minimal number of mutations, achieving an high catalytic
activity and high enantioselectivity. We found that, by introducing
two mutations W57G/R415A, detectable enzyme activity was achieved.
The rationally designed variant, W57F/R88H/V153S/K163F/I259M/R415A/V422A,
showed an improvement in reaction rate by more than 1716-fold toward
the bulky ketone under study, producing the corresponding enantiomeric
pure (S)-amine (enantiomeric excess (ee) value of >99%).
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