Four glycosyl transferases solubilized by detergents from Saccharomyces cerevisiae membranes have been tested for their specificity towards various polyprenols differing in chain length and saturation.
- 1The formation of dolichyl diphosphate-(N-acetylglucosamine)1-2 from uridine diphosphate N-acetylglucosamine and dolichyl monophosphate showed an obligatory requirement for α-saturated polyprenols. The apparent affinity for α-saturated polyprenyl phosphates improves with increasing chain length; those shorter than seven isoprene units were inactive.
- 2The rate of transfer of the chitobiosyl unit from dolichyl diphosphate chitobiose to the hexapeptide Tyr-Asn-Leu-Thr-Ser-Val followed the sequence: α-dihydropolyprenyl (C55) >(C80 > (C100).
- 3The enzyme transferring the mannosyl group from guanosine diphosphate mannose to dolichyl monophosphate also showed a clear dependence on α-saturation and chain length. In this case the chain length affects mainly the maximal velocity of the reaction. The highest value was obtained with C55α-dihydropolyprenyl phosphate (100 nmol × h−1× mg protein−1), whereas the value with C35α-dihydropolyprenyl phosphate was only 8 nmol × h−1× mg protein.−1.
- 4The mannosyl transfer from dolichyl monophosphate mannose to dinitrophenylated tetrapeptide Asn-Ala-Thr-Vol to form on O-glycosidic bond strongly depended on α-saturation and chain length of the polyprenyl phosphate. The rate of transfer correlated directly with the length of the polyprenyl residue. With C80α-dihydropolyprenol less than half the rate of the C100 compound was observed, whereas C55 and C35α-dihydropolyprenol are only 20 and 10% as active, respectively.