The principal goal of this research is a fundamental molecular understanding of the active site structure and catalytic mechanism(s) of copper containing amine oxidases. These enzymes are involved in the metabolism of biogenic primary amines, which have a variety of physiological functions in the cardiovascular, gastrointestinal, and nervous systems; amine oxidases are also responsible for the crosslinking of connective tissue (elastin and collagen) in aorta, lung, and cartilage. It is proposed to exploit the spectroscopic properties of the Cu(II) ion as a built in probe of the active site in amine oxidases purified from several sources. Variable temperature absorption, circular dichroism, magnetic circular dichroism, and emission spectroscopy as well as resonance raman and X-ray absorption spectroscopy will be employed. These spectroscopic techniques will also be used to determine how the Cu(II) interacts with any additional cofactor present in amine oxidases. Data will be obtained on the native, reduced, and copper-depleted forms of the enzymes. Effects of inhibitors, substrates, and substrate analogs on the spectra will be measured. Metal-substituted enzymes will be prepared to afford additional spectroscopic probes and to directly test possible metal ion roles in catalysis.