  Algebra of the constraints of twistor-like p-branes restoring 3/4 fraction of
the spontaneously broken D=4 N=1 supersymmetry is studied using the conversion
method. Classical and quantum realizations of the BRST charge, unified
superalgebra of the global generalized superconformal OSp(1|8) and Virasoro and
Weyl symmetries are constructed. It is shown that the quantum Hermitian BRST
charge is nilpotent and the quantized OSp(1|8) superalgebra is closed.
