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Enzymes in the Environment: Activity, Ecology and Applications - Chapter 11

Enzyme đất hoặc là chủ động tiết ra bởi các vi sinh vật sống và các rễ cây hoặc phát hành sau cái chết của sinh vật đất ly giải tế bào. Một lớp học của các enzyme, hydrolases, có một vai trò rất quan trọng trong các chu trình sinh địa hoá của các yếu tố chủ yếu (C, N, P, và S) từ các chất nền của họ trong đất chủ yếu là trong một hình thức polyme. Thông thường, các vi sinh vật (và rễ cây) có thể không mất các đại phân tử trực tiếp từ. | 11 Enzyme Adsorption on Soil Mineral Surfaces and Consequences for the Catalytic Activity Herve Quiquampoix Institut National de la Recherche Agronomique Montpellier France Sylvie Servagent-Noinville and Marie-Hélène Baron Centre National de la Recherche Scientifique Université Paris VI Thiais France I. INTRODUCTION Soil enzymes are either actively secreted by living microorganisms and plant roots or released after the death of soil biota by cell lysis. One class of enzymes the hydrolases have a very important role in the biogeochemical cycles of major elements C N P and S since their substrates in soil are mainly in a polymerized form. Usually microorganisms and plant roots cannot take up macromolecules directly from the external medium. There are few exceptions to this such as the uptake of fragments of deoxyribonucleic acid DNA or plasmids that lead to transformation in bacteria. In general the membrane transport systems are specific and recognize the universal biological monomers such as amino acids sugars and nucleotides low number oligomers such as cellobiose or maltose or mineral ionic groups that can be released by enzymatic hydrolysis of organic molecules such as orthophosphate and sulfate. Extracellular enzymes perform three main functions in soil 1 they reach substrates in pores with dimensions roughly 100 times smaller than those of bacteria 2 they hydrolyze these substrates and make them soluble and consequently able to diffuse back to the microorganisms or plant roots and at the same time 3 they transform polymers into monomers or oligomers that can be recognized and taken up by membrane transport systems to undergo intracellular metabolism. As enzymes are proteins they share with this class of macromolecules their strong affinity with interfaces. Proteins are potentially flexible polypeptide chains even if they have a stable folded configuration in solution with individual amino acids whose lateral chains have various physicochemical properties .