TAILIEUCHUNG - Báo cáo khoa học: Poly(silicate)-metabolizing silicatein in siliceous spicules and silicasomes of demosponges comprises dual enzymatic activities (silica polymerase and silica esterase)

Siliceous sponges can synthesize poly(silicate) for their spicules enzymati-cally using silicatein. We found that silicatein exists in silica-filled cell organelles (silicasomes) that transport the enzyme to the spicules. We show for the first time that recombinant silicatein acts as a silica polymerase and also as a silica esterase. | ễFEBS Journal Poly silicate -metabolizing silicatein in siliceous spicules and silicasomes of demosponges comprises dual enzymatic activities silica polymerase and silica esterase Werner E. G. Muller1 Ute SchloBmacher1 Xiaohong Wang2 Alexandra Boreiko1 David Brandt1 Stephan E. Wolf3 Wolfgang Tremel3 and Heinz C. Schroder1 1 Institut fur Physiologische Chemie Abteilung Angewandte Molekularbiologie Universitat Mainz Germany 2 NationalResearch Center for Geoanalysis Beijing China 3 Institut fur Anorganische Chemie Universitat Mainz Germany Keywords poly silicate silica esterase silica polymerase silicatein sponges Correspondence W. E. G. Muller Institut fur Physiologische Chemie Abteilung Angewandte Molekularbiologie Universitat Duesbergweg 6 55099 Mainz Germany Fax 49 6131 39 25243 Tel 49 6131 39 25910 E-mail wmueller@ Website http Siliceous sponges can synthesize poly silicate for their spicules enzymatically using silicatein. We found that silicatein exists in silica-filled cell organelles silicasomes that transport the enzyme to the spicules. We show for the first time that recombinant silicatein acts as a silica polymerase and also as a silica esterase. The enzymatic polymerization polycondensation of silicic acid follows a distinct course. In addition we show that silicatein cleaves the ester-like bond in bis p-aminophenoxy -dimethylsilane. Enzymatic parameters for silica esterase activity are given. The reaction is completely blocked by sodium hexafluorosilicate and E-64. We consider that the dual function of silicatein silica polymerase and silica esterase will be useful for the rational synthesis of structured new silica biomaterials. Received 22 October 2007 revised 13 November 2007 accepted 26 November 2007 doi Silicon is the second most common element in the Earth s crust 1 it possesses semi-metallic as well as metalloid properties. Silicon exists in nature in combination with oxygen as .

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