%0 Journal Article %A Appleyard, Geoffrey %A Davis, Gillian B. %T Activation of Sendai Virus Infectivity by an Enzyme in Chicken Amniotic Fluid %D 1983 %J Journal of General Virology, %V 64 %N 4 %P 813-823 %@ 1465-2099 %R https://doi.org/10.1099/0022-1317-64-4-813 %K enzyme %K Sendai virus %K infectivity %K amniotic fluid %I Microbiology Society, %X SUMMARY Sendai virus grown in LLC-MK2 cells is known to have low infectivity, no detectable haemolysing ability and predominantly uncleaved F glycoprotein. Treatment of such virus with chicken amniotic fluid resulted in a 103- to 104-fold increase in infectivity, the development of haemolysing ability, and cleavage of the F glycoprotein. The ‘Sendai activating enzyme’ (SAE) responsible for these effects required the presence of 1 mm-Ca2+ ions for maximum activity. It was inhibited by phenylmethylsulphonyl fluoride and soybean trypsin inhibitor but was unaffected by sulphydryl-blocking agents. The results of gel filtration tests suggested that the molecular weight of SAE was about 55000. SAE may be the natural proteolytic activator of Sendai virus in a soluble form. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-64-4-813