Sialic acid lyase in differentiating murine teratocarcinoma cells

N-Acetylneuraminic acid lyase (NAN-lyase) activity has been found to be much higher in the differentiated, murine parietal endodermal cell (PYS-2) in culture than in the related, undifferentiated embryonal teratocarcinoma cell (F9). The level of the enzyme rapidly increases in F9 cells exposed to an inducer of differentiation such as retinoic acid (RA) (10(-7) M). The level of the enzyme increases during log phase of growth of PYS-2 cells and decreases after the cells reach confluence. NAN-lyase from PYS-2 cells has been purified 365-fold and has been partially characterized. While most of the enzyme is freely soluble, at least 16% of the enzyme in PYS-2 cells is associated with the nucleus. The possible function of NAN-lyase in the cell and the significance of its marked elevation during growth and differentiation are discussed in view of the fact that the levels of NAN, neuraminidase, NAN transferases and the enzymes that synthesize and activate NAN, remain essentially unchanged during differentiation.