Catalyzes the conversion of 3-dehydroshikimate to protocatechuate (3,4-dihydroxybenzoate), a common intermediate of quinate and shikimate degradation pathways. 3-dehydroshikimate = 3,4-dihydroxybenzoate + H2O Requires a divalent metal cation for DSD activity, with a preference for Co(2+) but can also use Ni(2+), Mn(2+) and Mg(2+). kcat is 163.6 sec(-1). Aromatic compound metabolism; 3,4-dihydroxybenzoate biosynthesis. Homodimer. Consists of a fusion of two distinct domains: an N-terminal sugar phosphate isomerase-like domain associated with DSD activity and a C-terminal hydroxyphenyl-pyruvate dioxygenase-like domain. This C-terminal domain does not show any 4-hydroxyphenylpyruvate dioxygenase (HPPD) or protocatechuate dioxygenase (PCD) activity, but appears to be important for optimal DSD activity of QuiC1 in vivo. Belongs to the bacterial two-domain DSD family.