Читать книгу Enzyme-Based Organic Synthesis - Cheanyeh Cheng - Страница 38

The fundamental roles played by kinases in cells are in different signal transduction pathways and in many cellular processes such as cell metabolism, division, differentiation, survival and apoptosis, as well as development and oncogenesis. They effectively catalyzed the transfer of the γ‐phosphoryl group (PO₃ ^–) of ATP to a broad number of hydroxyl group containing substrates with the release of a proton (Scheme 3.11) [41]. Nowadays, the structural study of many different kinase classes indicates that all kinases present a similar nucleotide‐binding sequence [42].

Scheme 3.11 The transfer of γ‐phosphoryl group from ATP to hydroxyl group containing substrates by kinases.

Source: Chapman and Wong [41].

Protein crystallography in the solid state and ¹⁹F NMR in solution have elucidated the formation of a trigonal bipyramidal transition state with phosphorus fully bonded to three equatorial oxygens and partially bonded to axial donor’s oxygen and acceptor’s oxygen [43]. The hydrolysis of ATP to form ADP and P_i is highly exergonic that is used to drive the synthesis of information‐rich macromolecules, the transport of solute across membranes, and motion produced by muscle contraction.

Although most of the studies concerning about the phosphoryl group transfer using kinases are in vivo processes, there still some in vitro applications in organic synthesis. For instance, pyridoxal‐5′‐phosphate (PLP), a cofactor for enzymes catalyzing transaminations, decarboxylations, racemizations, and β‐ and γ‐carbon elimination/replacements, and are mostly associated with amino acid metabolism, can be synthesized in vitro through the phosphorylation of toxic antimetabolite l‐4‐hydroxythreonine (4HT) into 4‐phosphohydroxy‐l‐threonine (4PHT) by members of a novel kinase family DUF1537 (Scheme 3.12) [44].

Another example of the application of phosphorylation is about the bioinspired peptides containing 3 ser‐ser‐asp repeat motif (R‐SSD3) that was designed by mimicking the highly phosphorylated protein, dentin phosphophoryn (DPP), found in dentin and alveolar bone. Then, the R‐SSD3 peptides are sequentially phosphorylated at multiple serine sites in (DSS) _n sequence by casein kinases (CK1 and CK2) as shown in Scheme 3.13. These phosphorylated peptides were further used to induce biomimetic calcium phosphate mineralization of collagen fibrils that successfully produce biomimetic composite nanofibrils with integrated organic and inorganic phases [45].

Scheme 3.12 Phosphorylation of 4HT to 4PHT by kinase DUF1537 for enzyme cofactor PLP biosynthesis.

Source: Modified from Thiaville et al. [44].

Scheme 3.13 Sequential phosphorylation of peptide R‐SSD3 with casein kinases.