  The paper analyzes the problem fixing the local fermionic gauge symmetry in
the Green-Schwarz superstring theory,related to the covariant quantization of
this theory.The gauge-fixing procedure reveals the connection between GS and
NSR formalisms, conjectured earlier. The analysis relates the kappa-invariance
to the Bogomol'ny-type condition,well-known in connection with D-brane
theories. The BPS saturation condition appears to be a target space
superpartner of the kappa-invariance condition. Relation to RR charges of
p-brane solutions of the ten-dimensional supergravity is discussed.
