Citrate metabolism

Figure 10.31 Citrate metabolism by Lactococcus lactis ssp. lactis biovar. diacetylactis or Leuconostoc spp. (from Cogan and Hill, 1993).

Bott, M. Meyer, M. Dimroth, P. Regulation of anaerobic citrate metabolism in Klebsiella pneumoniae. Mol. Microbiol., 18, 533-546 (1995)... 

Once citrate enters the cell, it is degraded to pyruvate, acetate, and carbon dioxide (Figure 13.8). Citrate lyase, one of the enzymes required for citrate metabolism, is induced by citrate in Leuconostoc spp. and heterofermentative lactobacilli (Mellerick and Cogan 1981). Since pyruvate is formed from citrate without the simultaneous production of reduced NAD, it does not have to be diverted to reoxidizing NAD, as is true for pyruvate formed from sugar fermentation. This surplus ... 

Cogan, T. M. 1981. Constitutive nature of the enzymes of citrate metabolism in Streptococcus lactis subsp. diacetylactis. J. Dairy Res. 48, 489-495. 

Contents I. Introduction 168 II. Sampling Techniques 168 III. Compositional Analysis 169 A. Moisture and total solids 169 B. Fat 171 C. Protein 171 D. Ash 172 E. Salt and chloride content 172 F. Acidity and pH 172 G. Calcium and phosphorus 173 IV. Monitoring Cheese Ripening 173 A. Assessment of lactose, lactate, and citrate metabolism 174 B. Assessment of lipolysis 178 C. Assessment of proteolysis 180 D. Assessment of smaller breakdown products 194 V. Novel and Rapid Instrumental Methods 196 VI. Concluding Remarks 200 References 201... 

Oteiza PI, Keen CL, Han B, et al. 1993. Aluminum accumulation and neurotoxicity in Swiss-Webster mice after long-term dietary exposure to aluminum and citrate. Metabolism 42 1296-1300. 

Knowledge of phosphorus and citrate metabolism in vitamin D poisoning and in idiopathic hypercalcemia of infancy is very incomplete and somewhat contradictory, but in certain respects the changes in these electrolytes in these two disorders may differ. 

Bowman, R.H. (1964). Inhibition of citrate metabolism by sodium fluoroacetate in the perfused rat heart and the effect on phos-phofructokinase activity and glucose utilization. Biochem. J. 93 13-15. 

The enterococci contribute to the ripening and aroma development of cheese due to their proteolytic and esterolytic activities, as well as their diacetyl production by citrate metabolism (Centeno et al. 1999). The presence and growth of enterococci in cheeses and sausages results in organoleptically unique products, which contribute to the local cuisine and the region s heritage. Due to interlinked European and worldwide markets, these cheeses are widely distributed and are internationally considered as delicacies (Franz et al. 1999). 

The fact that the bone tissue has a very high citrate content (C12) and that many factors, such as vitamin D or parathormone, act both on calcium and citrate metabolism, explains the importance of altered citrate concentration in blood and urine during bone diseases. Such alterations will not, however, be considered here, as they have been previously reviewed elsewhere (H8, L9, Nil). 

Figure 8.2 Pyruvate branch with diacetyl production and citrate metabolism. Underline indicates reactions that have to be modified to increase diacetyl production (for further explanation, see text).

Carbonyl compounds typically are significant to the flavor of most fermented food products. As has been shown, these carbonyls may arise due to carbohydrate or citrate metabolism, lipid oxidation or amino acid degradation. 

Citrate metabolism—The level of citrate in the blood decreases in a vitamin D deficiency. Citrate is an important organic acid involved in many metabolic functions, including mobilization of minerals from bone tissue and removal of calcium from the blood. 

The effect on citrate metabolism is thought to be due to changes in mineral metabolism brought about by the absence or presence of vitamin D rather than to a direct action of the vitamin on the formation of citrate. 

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