Poly(silicate)-metabolizing silicatein in siliceous spicules and silicasomes of demosponges comprises dual enzymatic activities (silica polymerase and silica esterase) |
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Authors: | Müller Werner E G Schlossmacher Ute Wang Xiaohong Boreiko Alexandra Brandt David Wolf Stephan E Tremel Wolfgang Schröder Heinz C |
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Institution: | Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universit?t, Duesbergweg 6, Mainz, Germany. wmueller@uni-mainz.de |
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Abstract: | 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. |
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