Biocatalysis Fueled by Light: On the Versatile Combination of Photocatalysis and Enzymes

Abstract

Enzymes catalyze a plethora of highly specific transformations under mild and environmentally benign reaction conditions. Their fascinating performances attest to high synthetic potential that is often hampered by operational obstacles such as in vitro cofactor supply and regeneration. Exploiting light and combining it with biocatalysis not only helps in overcoming these drawbacks, but the fruitful liaison of these two fields of “green chemistry” also offers opportunities to unlock new synthetic reactivities. In this review we provide an overview of the wide variety of photo‐biocatalysis, ranging from the photochemical delivery of electrons required in redox biocatalysis and photochemical cofactor and reagent (re)generation to direct photoactivation of enzymes enabling reactions unknown in nature. We highlight synthetically relevant transformations such as asymmetric reactions facilitated by the combination of light as energy source and enzymes’ catalytic power.

Design and Evaluation of Artificial Hybrid Photoredox Biocatalysts

“…[8,9] Based on the success of artificial metalloenzyme engineering, there is growing interest in expanding the scope of artificial cofactors to encompass other catalytic modalities. [10,11] For example, photoredox catalysis has shown increased application for chemical synthesis due to its broad utility in bond activation through mechanisms that are often orthogonal or complementary to traditional transition metal chemistry. [12,13] Photoredox transformations operate through photoinduced electron transfer (PET) events, which facilitate the generation of highly reactive intermediates at ambient temperature bypassing thermal barriers and permitting access to unique reactivity patterns.…”

Recent developments in enantioselective photocatalysis

“…One method to extend their reactivity is to use them in combination with photocatalysis. There are now many examples that employ this strategy for both racemic and enantioselective transformations and these are well covered in Gulder's review [7]. One of the earliest enantioselective examples was reported by Hyster et al for the dehalogenation of halolactones 421 in the presence of ketoreductases (KREDs) and NADPH (Scheme 71) [167].…”

“…This review aims to cover the seminal work within enantioselective photocatalysis but with a focus on the most recent devel-opments. There have been a number of reviews on or closely related to this topic, so this review will not contain an exhaustive list of all enantioselective photocatalytic reactions; however, this review does aim to cover the different strategies that have been developed [5][6][7][8][9][10][11][12][13][14][15][16]. There is a subset of reactions that achieve asymmetry via a stepwise photochemical process followed by a separate enantioselective catalysis step that will not be covered in this review [17][18][19].…”

Light‐driven catalysis with engineered enzymes and biomimetic systems

“…Recently, several aspects of this topic have been reviewed. These reviews include strategies toward pairing natural enzymes with a variety of photosensitizers, using light to fuel cofactor regeneration, and building in vivo mechanisms for photobiocatalysis [41][42][43][44]. In addition, new directions to combine photocatalysis and biocatalysis are constantly emergent, such as using photoexcitation to promote promiscuous activities in naturally occurring enzymes [45,46].…”