The deoxyribonucleic acid polymerases from the diatom Cylindrotheca fusiformis. Partial purification and characterization of four distinct activities

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Abstract
Four extramitochondrial DNA polymerases [EC 2.7.7.7] from the marine photosynthetic diatom C. fusiformis were isolated and purified more than 1200-fold by chromatography on DNA-cellulose and DEAE-Sephadex. The enzymes were equally susceptible to inhibition by the thiol-blocking agents N-ethylmaleimide and p-chloromercuribenzoate, the zinc chelator o-phenanthroline, and the nuclei acid interchelators ethidium bromide and acriflavin; they displayed similar pH optima, preferred activated DNA, and had strict dependence on high K+ for maximum activity. They were differentiated on the basis of their kinetic parameters, template-primer utilization and salt requirements. The 4 activities varied with the growth stage of C. fusiformis. Activities of polymerases A and D doubled in exponential-phase cells as compared with those in stationary-phase cells, and the increase in polymerase B and chloroplast activity C was 20-40%. The relationship of the diatom polymerases to the complements in other organisms [eukaryotes] is discussed.