Acquisition of Structure-guiding and Structure-forming Properties during Maturation from the Pro-silicatein to the Silicatein Form

Schröder, Heinz C.; Wang, Xiaohong; Manfrin, Alberto; Yu, Shu‐Hong; Grebenjuk, Vlad A.; Korzhev, Michael; Wiens, Matthias; Schloßmacher, Ute; Müller, Wernér E.G.

doi:10.1074/jbc.m112.351486

Cited by 35 publications

(45 citation statements)

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“…To acquire this enzyme, a synthetic vector containing cDNA encoding for the mature wildtype Silα from Suberites domencula, fused to an N-terminal hexahistidine tag and codon optimized for expression in Escherichia coli, was used. It is known that the mature form of the protein is highly hydrophobic and difficult to produce in soluble form (16,18). Thus, in attempts to improve its solubility the gene was also subcloned with the sequences for a number of proteins known to enhance solubility and folding.…”

Section: Resultsmentioning

confidence: 99%

“…In contrast, poriferans (marine sponges) that use silica as part of their inorganic skeleton use a family of enzymes termed the silicateins to catalyze the polymerization of soluble silicates into silica (14)(15)(16). The primary sequences of these enzymes have been reported and they bear a remarkable homology with proteases of the cathepsin family, with ∼65% sequence similarities and ∼50% sequence identities relative to cathepsin L. Both enzymes share a similar Xaa-His-Asn catalytic triad at their active site, although in the silicateins a Ser residue occupies the Xaa position rather than Cys in cathepsin L. Previous reports have shown that silicatein-α (Silα), the prototypical member of this family, can catalyze the hydrolysis of ethoxysilanes such as tetraethoxysilane (TEOS) and triethoxyphenylsilane (17).…”

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confidence: 99%

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Recombinant silicateins as model biocatalysts in organosiloxane chemistry

Dakhili

Caslin

Faponle

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The family of silicatein enzymes from marine sponges (phylum Porifera) is unique in nature for catalyzing the formation of inorganic silica structures, which the organisms incorporate into their skeleton. However, the synthesis of organosiloxanes catalyzed by these enzymes has thus far remained largely unexplored. To investigate the reactivity of these enzymes in relation to this important class of compounds, their catalysis of Si-O bond hydrolysis and condensation was investigated with a range of model organosilanols and silyl ethers. The enzymes' kinetic parameters were obtained by a high-throughput colorimetric assay based on the hydrolysis of 4-nitrophenyl silyl ethers. These assays showed unambiguous catalysis with k cat /K m values on the order of 2-50 min. Condensation reactions were also demonstrated by the generation of silyl ethers from their corresponding silanols and alcohols. Notably, when presented with a substrate bearing both aliphatic and aromatic hydroxy groups the enzyme preferentially silylates the latter group, in clear contrast to nonenzymatic silylations. Furthermore, the silicateins are able to catalyze transetherifications, where the silyl group from one silyl ether may be transferred to a recipient alcohol. Despite close sequence homology to the protease cathepsin L, the silicateins seem to exhibit no significant protease or esterase activity when tested against analogous substrates. Overall, these results suggest the silicateins are promising candidates for future elaboration into efficient and selective biocatalysts for organosiloxane chemistry.silicatein | biocatalysis | organosilicon | organosiloxane | silyl ether T he organosiloxanes, compounds containing C-Si-O moieties, represent a class of compounds with a truly diverse range of applications. They are commonly used in the form of polysiloxane "silicone" polymers as components of industrial and consumer products for a variety of purposes such as bulking agents, separation media, protective coatings, lubricants, emulsifiers, and adhesives (1-3). Their use as auxiliaries in the chemical synthesis of complex molecules is also long-established (4-6). However, the production and synthetic manipulation of these compounds are almost entirely dependent on chlorosilane feedstocks, which are environmentally undesirable and energyintensive to produce (7,8). Furthermore, organosiloxanes, which are entirely anthropogenic in origin, are now known to be persistent environmental contaminants because little attempt is made to recover and recycle them (3). Synthetic routes that use, and ultimately recycle, siloxanes and silanols as alternatives would in principle be more environmentally sound.One possible strategy toward improved sustainability is to harness enzymes for chemical processing. Such biocatalysts are attractive because they offer highly efficient synthesis in terms of yields and regio-and stereospecificity, together with an ability to promote reactions under mild conditions and a minimal reliance on halogenated or metallic feedstocks (...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Recombinant silicateins as model biocatalysts in organosiloxane chemistry

Dakhili

Caslin

Faponle

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Even more, the enzyme itself, silicatein is not only a catalytically active protein, but also a structure-giving backbone for the primordial/growing bio-silica fibrils [133]. Studying the maturation process of silicatein on a molecular level if it became overt that the enzyme acquires these properties (to be enzymatically active and to be structure-guiding) during the maturation, from the pro-silicatein to the active enzyme, a process during which the propeptide is split off from the inactive precursor [134]. During this hydrolytic cleavage, the active enzyme undergoes a conformational change that the molecule becomes less soluble and precipitates.…”

Section: Scaffoldmentioning

confidence: 99%

The Deep-Sea Natural Products, Biogenic Polyphosphate (Bio-PolyP) and Biogenic Silica (Bio-Silica), as Biomimetic Scaffolds for Bone Tissue Engineering: Fabrication of a Morphogenetically-Active Polymer

et al. 2013

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Bone defects in human, caused by fractures/nonunions or trauma, gain increasing impact and have become a medical challenge in the present-day aging population. Frequently, those fractures require surgical intervention which ideally relies on autografts or suboptimally on allografts. Therefore, it is pressing and likewise challenging to develop bone substitution materials to heal bone defects. During the differentiation of osteoblasts from their mesenchymal progenitor/stem cells and of osteoclasts from their hemopoietic precursor cells, a lineage-specific release of growth factors and a trans-lineage homeostatic cross-talk via signaling molecules take place. Hence, the major hurdle is to fabricate a template that is functioning in a way mimicking the morphogenetic, inductive role(s) of the native extracellular matrix. In the last few years, two naturally occurring polymers that are produced by deep-sea sponges, the biogenic polyphosphate (bio-polyP) and biogenic silica (bio-silica) have also been identified as promoting morphogenetic on both osteoblasts and osteoclasts. These polymers elicit cytokines that affect bone mineralization (hydroxyapatite formation). In this manner, bio-silica and bio-polyP cause an increased release of BMP-2, the key mediator activating the anabolic arm of the hydroxyapatite forming cells, and of RANKL. In addition, bio-polyP inhibits the progression of the pre-osteoclasts to functionally active osteoclasts. Based on these findings, new bioinspired strategies for the fabrication of bone biomimetic templates have been developed applying 3D-printing techniques. Finally, a strategy is outlined by which these two morphogenetically active polymers might be used to develop a novel functionally active polymer.

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“…Therefore, the is a strong interest in alternative scaffold materials allowing the fabrication of 3D scaffolds by 3D printing without (post)sintering. One candidate might be biosilica that can be hardened by applying a bioinspired method mimicking the hardening of "soft" biosilica initially formed during sponge spicule formation, based on addition of poly(ethylene glycol) (PEG) as "binder" (see below, Schröder et al 2012a). …”

Section: D Printingmentioning

confidence: 99%

Inorganic Polymers: Morphogenic Inorganic Biopolymers for Rapid Prototyping Chain

Müller

Schröder

Shen

et al. 2013

Biomedical Inorganic Polymers

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In recent years, considerable progress has been achieved towards the development of customized scaffold materials, in particular for bone tissue engineering and repair, by the introduction of rapid prototyping or solid freeform fabrication techniques. These new fabrication techniques allow to overcome many problems associated with conventional bone implants, such as inadequate external morphology and internal architecture, porosity and interconnectivity, and low reproducibility. However, the applicability of these new techniques is still hampered by the fact that high processing temperature or a postsintering is often required to increase the mechanical stability of the generated scaffold, as well as a post-processing, i.e., surface modification/functionalization to enhance the biocompatibility of the scaffold or to bind some bioactive component. A solution might be provided by the introduction of novel inorganic biopolymers, biosilica and polyphosphate, which resist harsh conditions applied in the RP chain and are morphogenetically active and do not need supplementation by growth factors/cytokines to stimulate the growth and the differentiation of bone-forming cells.

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Acquisition of Structure-guiding and Structure-forming Properties during Maturation from the Pro-silicatein to the Silicatein Form

Cited by 35 publications

References 46 publications

Recombinant silicateins as model biocatalysts in organosiloxane chemistry

Recombinant silicateins as model biocatalysts in organosiloxane chemistry

The Deep-Sea Natural Products, Biogenic Polyphosphate (Bio-PolyP) and Biogenic Silica (Bio-Silica), as Biomimetic Scaffolds for Bone Tissue Engineering: Fabrication of a Morphogenetically-Active Polymer

Inorganic Polymers: Morphogenic Inorganic Biopolymers for Rapid Prototyping Chain

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