硅蛋白的发现导致了生物无机化学范式的转变,因为它是第一个可以催化无机单体合成无机聚合物分子的酶.分子生物学,生物化学和细胞生物学数据证实,两种硅质海绵动物,包括寻常海绵和六放海绵,它们的骨针都是由硅蛋白/酶催化合成的.这种酶不仅存在于硅质海绵骨针内部,而且也存在于硅质海绵骨针表面.在硅质海绵骨针生长过程中,它催化生物二氧化硅的合成而构建硅薄层,一层层的硅薄层逐步沉积从而形成硅质海绵骨针.寻常海绵动物Suberites domuncula体外实验获得的硅蛋白活性数据(催化生物二氧化硅的形成)反映了体内骨针生长所需的生物二氧化硅量.本文最后总结了在寻常海绵动物骨针生长和成熟过程中出现的生物熔合现象,即内部的硅薄层“烧结”在一起形成致密的硅棒.强壮的和坚硬的生物二氧化硅骨架的形成需要经历一个硬化过程,这个过程由海绵动物排水通道表面的细胞膜控制,排除生物二氧化硅缩聚反应过程中释放出的水分而使材料固化.%The discovery of silicatein caused a paradigm shift,since it is the first enzyme which catalyzes the synthesis of a polymeric inorganic molecule from inorganic monomers.Molecular biological,biochemical and cellbiological data showed that the synthesis of siliceous spicules in both demosponges and hexactinellids is enzymatically driven via silicatein.This enzyme exists both intra-spicularly and in the extra-spicular space.It catalyzes the formation of bio-silica constituting the silica lamellae that are formed during the appositional (layer-bylayer) growth of the spicules.The extent of (bio-silica forming) activity of silicatein from the demosponge Suberites domuncula measured in vitro reflects the amount of bio-silica required for the formation of spicules in vivo.It is furthermore summarized that during growth and maturation of the spicules in demosponges a bio-fusion process occurs that results in an intra-spicular sintering of the silica lamellae to form compact silica rods.Finally we report that for the formation of the strong and stiff bio-silica skeleton of sponges a hardening process is required that is (presumably) driven by cell-membrane bound aquaporin channels which allow the removal of water,which is released during the bio-silica polycondensation reaction.
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