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Ultraviolet spectra of thermolysin on mixing with n-alkyl ketones were investigated. Hypochromic effect of UV spectra of enzyme and model compounds was observed. A clear batho-chromic shift (red shift) of thermolysin spectrum was also demonstrated. With increase in chain length of ketones, the red shift was found reduced. The hypochromic and bathochromic effects were significantly suppressed when enzyme or model compounds were pre-treated with inhibitor (phosphor-amidon). There had been no such effect of ketones upon mixing with substrates. It was speculated that ketones interact with the UV sensitive aromatic amino acid residues at the microenvironment of active site of enzyme.

Inhibitory activity of glucosamine derivatives against angiotensin I converting enzyme (ACE) was investigated. Many N-substituted glucosamine derivatives were synthesized via 1,3,4,6-tetra-O-acetyl-glucosamine hydrochloride. Among them, N-(phenylalanyl-alanyl-prolyl)-glucosamine was found to be the most effective for ACE inhibition, and the half inhibitory concentrations (IC50_) was estimated as 300μM. Furthermore, N-(3,7-dimethyl-2(E/Z), 6-hexadien-carbonyl)-glucosamine and N-(p-dimethylamino benzoyl)-glucosamine were found to be effective for the inhibition of ACE, and their IC50 values were estimated as 5 mM and 8 mM, respectively.