Enzymatic analysis using substrates that yield fluorescent precipitates

A substrate of the formula:

• (BLOCK-O-)-X.sub.n
• where BLOCK is a blocking group that is a monovalent moiety derived by removal of a hydroxy group from phosphate or sulfate, or a biologically compatible salt thereof;
• or a monovalent moiety derived by removal of a hydroxy group from a carboxy group of an aliphatic, aromatic or amino acid or of a peptide;
• or a monovalent moiety derived by removal of an anometic hydroxy group from a mono- or polysaccharide;
• and is capable of being cleaved from the remainder of the substrate by action of a specific enzyme resulting in a visible precipitate of the formula:
• H-O-X.sub.fl
• where X.sub.fl has the structure:
• ##STR20## where carbon atoms of --C.sup.1 .dbd.C.sup.2 -- are further joined so as to complete a first 5- or 6-membered aromatic ring which may contain at least one of the hetero atoms N, O or S,
• where carbon atoms of --C.sup.4 --N.dbd.C.sup.3 -- are further joined so as to complete a second 5- or 6-membered aromatic ring that contains at least the nitrogen between C.sup.3 and C.sup.4 and may contain at least one additional hetero atom N, O or S,
• where the first and second aromatic rings may be joined by a 5- or 6-membered bridging ring that contains at least the C.sup.2 from the first aromatic ring and the C.sup.3 from the second aromatic ring, which bridging ring may be saturated or unsaturated and may contain a hetero atom N, O, or S,
• where each of the first and second aromatic rings may be fused to at least one additional aromatic ring that may contain at least one of the hetero atoms N, O or S, and
• where each of said aromatic rings may be further modified by substitution of any hydrogens on an aromatic carbon by substituents that are halogen, nitro, cyano, aryl, lower alkyl (1-4 carbons), perfluoroalkyl (1-4 carbons), or alkoxy (1-4 carbons), or any combination thereof;
• and
• X.sub.fl is covalently linked to the oxygen --O-- at C.sub.1.