Reusch R N
Department of Microbiology, Michigan State University, East Lansing 48824.
FEMS Microbiol Rev. 1992 Dec;9(2-4):119-29. doi: 10.1111/j.1574-6968.1992.tb05829.x.
Short-chain complexed poly-beta-hydroxybutyrate, 130-170 monomer units, is a ubiquitous constituent of cells, wherein it is usually associated with other macromolecules by multiple coordinate bonds, or by hydrogen bonding and hydrophobic interactions. This conserved PHB has been isolated from the plasma membranes of bacteria, from a variety of plant tissues, and from the plasma membranes, mitochondria, and microsomes of animal cells. In bacterial membranes, PHB has been found complexed to the calcium salts of inorganic polyphosphates, and to single-stranded DNAs. The ability of PHB to solvate salts, consisting of cations having high solvation energies and large delocalized anions, is in accordance with its molecular characteristics, that of a flexible linear molecule possessing a large number of electron-donating ester oxygens suitably spaced to replace the hydration shell of cations. In turn, PHB may be rendered soluble in aqueous media by complexation to water-soluble proteins, such as serum lipoproteins and albumin. Such solvates are highly resistant to hydrolytic enzymes. These findings suggest that the physiological roles of this unique biopolymer may include the solvation of salts of polymeric anions to facilitate their movement through hydrophobic barriers, and the protection of cellular polymers from enzymatic degradation.
短链复合聚-β-羟基丁酸酯，由130 - 170个单体单元组成，是细胞中普遍存在的成分，在细胞中它通常通过多个配位键，或通过氢键和疏水相互作用与其他大分子结合。这种保守的聚-β-羟基丁酸酯已从细菌的质膜、多种植物组织以及动物细胞的质膜、线粒体和微粒体中分离出来。在细菌膜中，已发现聚-β-羟基丁酸酯与无机多磷酸盐的钙盐以及单链DNA结合。聚-β-羟基丁酸酯使由具有高溶剂化能的阳离子和大的离域阴离子组成的盐溶剂化的能力，与其分子特性相符，即它是一种柔性线性分子，拥有大量供电子的酯氧，其间隔适当，足以取代阳离子的水合壳。反过来，聚-β-羟基丁酸酯可通过与水溶性蛋白质（如血清脂蛋白和白蛋白）络合而溶于水性介质。这种溶剂化物对水解酶具有高度抗性。这些发现表明，这种独特生物聚合物的生理作用可能包括使聚合阴离子的盐溶剂化，以促进其通过疏水屏障的移动，以及保护细胞聚合物免受酶促降解。
