MECHANISM OF INVOLVEMENT OF THE GLYCOLATE PATHWAY IN ACCUMULATION OF FREE PROLINE IN A MARINE CHLORELLA UNDER CONDITIONS OF SALINITY

To clarify the mechanism of involvement of the glycolate pathway in synthesis of free proline, we investigated the content and isotope composition (delta-C-13) of proline, carbohydrates, proteins, and dry biomass under conditions of salinity in cells of Chlorella stigmatophora Butcher during stimulation and inhibition of the glycolate pathway. Accumulation of free proline in Chlorella cells is shown to be inversely correlated with size of the carbohydrate pool, both during stimulation of the glycolate pathway by NaCl and during its inhibition by HPMS + INH. With respect to content of the isotopes C-12 and C-13 in it, the carbon skeleton of proline (delta-C-13) = -29 - -31.5 parts per thousand) was found to be similar to the carbon skeleton of carbohydrates (delta-C-13 = -29.3 - -32.6 parts per thousand) and significantly different from that of proteins (delta-C-13 = -42 - -47 parts per thousand). The delta-C-13 value of the starting CO2 was -21 parts per thousand. The C-12/C-13 ratio in proline and carbohydrates was analogous and depended on the rate of functioning of the glycolate pathway. Based on the obtained results, it is concluded that the glycolate pathway can be involved in synthesis of free proline through a carbon mechanism (carbohydrate metabolism).