290 BIOCHEMICAL SOCIETY TRANSACTIONS zy Wafles In the production of biscuits and waffles, gluten-weak flours are normally required. Previously there was no difficulty in obtaining such flours in Europe, but as more and more strong gluten varieties of wheat are grown in every country, this has become an area of some concern. High-gluten varieties of wheat intrinsically bind more water and this means that to achieve a lower viscosity, so as to make the dough manageable, additional water must be added. This water must be subsequently evaporated, leading to considerable energy expense and ad- ditional time. The addition of proteinase to batter can substantially reduce viscosity. For practical purposes the enzyme preparations may be added in the bakery itself or in the mill. The pH of the wafAe batter, which depends on the individual recipe, should be monitored and should not be too far from the optimum pH of the individual enzyme being used. The above review of an often-forgotten application of proteinases in this industry serves to illustrate the ever present biochemical application in these areas. Although these industries are small users of enzymes compared with the starch-processing industry, they nonetheless offer advantages and opportunities for small biochemical firms. zyxwv Belloc, A. (1975) zyxwvu US. Patent 3875006 (April zyxw 1) Dubois, D. K. (1980) Technical Bulletin 2, American Institute of Hasborg, E. ter (1981) Process Biochem. 16, 16-19 Miller, B. S. zyxwvut & Johnson, J. A. (1951) Arch. Biochem.Biophys. 32,200 Baking, Manhattan, KS Nutrition and protein turnover P. J. GARLICK, G. A. CLUGSTON, M. A. McNURLAN, V. R. PREEDY and E. B. FERN Clinical Nutrition and Metabolism Unit, 4 St. Pancras Way, London NWI 2PE, U.K. The protein mass of animal tissues is maintained by continuous balancing of the processes of protein synthesis and breakdown. This should not, however, be taken to imply that the rates of synthesis and breakdown are always equal, since even in a normal animal fluctuations in body and tissue protein content occur in response to the discontinuous intake of food. This is illustrated in Table 1, which shows the rates of synthesis, breakdown and oxidation of protein by the whole body of obese women in both the fed and the fasting states. Measurements were made continuously by constant infusion of [ l-14Clleucine over a 24 h period. During the first 12h the subjects were fed hourly, and for the remainder they fasted. When the diet contained a normal amount of energy (about 8.4MJ) and protein (about 70g) the rates of protein synthesis and oxidation were stimulated by feeding, but the rate of protein breakdown was depressed. The resultant effect of these changes is that during feeding there was net protein retention in the body tissues. Conversely, during fasting, a similar amount of protein to that retained during feeding was oxidized and lost from the body. We believe that the storage occurs by expansion of the protein content of one or more tissues, because the change in the concentration of free amino acid in the blood was insufficient to account for storage in this form (G. A. Clugston & P. J. Garlick, unpublished work). Table 1. Whole-body protein metabolism in obese women Rates of whole-body protein turnover were measured in four obese women by constant infusion of [1-'4C]leucine for 24h periods, including 12h of continuous feeding and 12h of fasting, as described by Garlick et al. (1980~). Measurements were made with the subjects receiving a normal diet and then after 3 weeks on a low-energy protein-free diet (data of Clugston & Garlick, 1981). Rates of whole-body protein metabolism zyxwvuts (g of protein/l2 h) Intake Synthesis Breakdown Oxidation A I > Normal diet Feeding 70 121 17 41 Fasting 0 92 112 20 Feeding 0 72 79 7 Protein-free diet Fasting 0 70 77 6 The response to feeding was different when a protein-free low-energy diet was given for 3 weeks (Table 1). Rates of protein synthesis and oxidation were much lower than rates on the normal diet, even than those observed during fasting. The rate of proteolysis, by contrast, was lower than that observed during fasting, but similar to that during feeding on the normal diet. The differences between the fed and fasting states, however, were completely eliminated by the protein-free diet, indicating the importance of dietary protein in the regulation of protein synthesis and breakdown in the whole body. The responses of the whole body to food intake are the net result of different changes in protein synthesis and breakdown in individual tissues. The difficulty of sampling has limited our knowledge of separate tissues in man, but in experimental animals much more is known. Table 2 shows the fractional rates of protein synthesis (percentage of tissue protein renewed by synthesis each day) in a number of tissues of young rats on a normal diet, and the responses to starvation for 2 days and to a protein-free diet for 9 days. These estimates were made by Table 2. Effect of nutrition on rates of protein synthesis and breakdown in tissue of young male rats Fractional rates of protein synthesis (%/day, ~s.E.M.) were estimated from the incorporation of label into protein lOmin after an injection of 15Opmol of [ 3H]phenylalanine/100g body wt. (M. A. McNurlan, V. R. Preedy, E. B. Fern & P. J. Garlick, unpublished work). Estimates of rates of protein breakdown (kd) in liver and muscle were calculated from synthesis rates (kJ and rates of change of protein mass (kJ, as described in the text, and are shown in parentheses. The values used for k, (%/day) taken from Garlick et al. (1975) were: in muscle, 6.0 (fed), 0 (starved) and -1.4 (protein-free) and in liver 6 (fed) 0 (starved) and -1 (protein-free). The proportion of liver synthesis that was exported was taken to be 38.2 (fed), 34.4 (starved) and 31.6 (protein-free) % (estimated from Pain et al., 1978a,b). Fractional rates of protein synthesis (%/day) Starved Protein-free r A \ Tissue Fed (2 days) (9 days) Jejunal mimosa 123 zyxwv f 4 (1 17) 92 + 3 95+6 Jejunal serosa 52 f 2 31f1 - Bone 90+2 62f3 - Liver 86 f 6 (47) 72 f 3 (47) 69 f 4 (48) Skin 64+2 47f2 - Heart 19.6 f 0 . 8 1 1.9 + 0.7 10.3 f 0.2 Gastrocnemius 16.9 5 0 . 6 (10.9) 5.9 +0.3 (5.8) 4.1 f 0 . 7 (5.5) muscle 1982