EFFECT OF HIGH PRESSURE ON THE ACCUMULATION OF IMP AND ON THE STABILITY OF AMP DEAMINASE IN RABBIT SKELETAL MUSCLE SUNAO MORI 1 , AKIKO UCHIDA 2 , SHUHEI YAMAMOTO 2 , ASMA SULTANA 1 , RYUICHI TATSUMI 1 , WATARU MIZUNOYA 1 , ATSUSHI SUZUKI 2 and YOSHIHIDE IKEUCHI 1,3 1 Department of Bioscience and Biotechnology Graduate School of Agriculture, Kyushu University Fukuoka 812-8581, Japan 2 Department of Applied Biological Chemistry Faculty of Agriculture, Niigata University Niigata 950-2181, Japan Accepted for Publication July 14, 2006 ABSTRACT This study evaluated the effect of high pressure on rabbit skeletal muscle, specifically on the production of inosinic acid (IMP), one of “umami” com- ponents, and on the activity of adenosine triphosphate (AMP) deaminase, which plays a role in the conversion of AMP to IMP. By increasing the pressure (0.1 to 300 MPa), nucleotide analysis showed that IMP content in muscle increased instantly with a concomitant decrease in ATP content. The IMP content of muscle at 300 MPa was approximately 15% higher than with lower pressures (0.1–200 MPa) when stored for 1 week at 4C after pressurization. These results suggested that the metabolism of nucleotides in muscle was not significantly impaired by pressure treatment. At 300 MPa, AMP deaminase maintained approximately 70% of the activity at 0.1 MPa. In contrast, the activity of purified AMP deaminase was completely lost at 200 MPa, and irreversible conformational changes were observed by in situ fluorescence spectroscopy. These results indicated that purified AMP deaminase was irre- versibly denatured under pressure as high as 300–400 MPa. 3 Corresponding author. TEL: +81-92-642-2949; FAX: +81-92-642-2949; EMAIL: ikeuchiy@ agr.kyushu-u.ac.jp Journal of Food Biochemistry 31 (2007) 328–342. All Rights Reserved. © 2007, The Author(s) Journal compilation © 2007, Blackwell Publishing 328