Lactate dehydrogenase molecular weight

Sutton [1.15] studied the question of how quickly solutions with certain CPAs (GL, dimethylsulfoxide (DMSO) and others] have to be cooled in order to avoid crystallization. At 100 °C/min concentration of 42.1 % DMSO and 48.5 % for GL are necessary to achieve the glass phase. With a 32.5 % solution of (2R.3R)-(-)butan-2,3-dio, the same effect can be accomplished at = 50 °C/min. In Fig. 1.18 Sutton (Fig. 11 from [1.114]) showed, that polyethylene glycol with a molecular weight of 400 (PEG 400) reduced the critical cooling rate down to approx. 25 °C/min. The addition of PEG 8000 [1.115] improved the protection of lactate dehydrogenase (LDH) by maltodextrins, if maltodextrins with low dextrose equivalents are used. 

Figure 2. SDS gel electrophoresis of the products of partial cystine cleavage for several test proteins. A. molecular weight standards, B. yeast alcohol dehydrogenase. C. P-lactoglobulin, D. hen egg lysozyme, E. ovalbumin, F. calf fetal serum fetuin. Molecular weight standards are indicated by arrows on the left side of the gel and are bovine serum albumin (66,300), bovine liver glutamate dehydrogenase (55,400), porcine muscle lactate ddiydiogenase (36,500), bovine erythrocyte carbonic anhydrase (31,000), soybean trypsin inhibitor (21,500), hen egg lysozyme (14,400), bovine lung aprotinin (6,000), unresolved bovine pancreatic insulin A and B chains.

Lactate dehydrogenase is a pyridine nucleotide oxidoreductase, a tetramer of 140 kD molecular weight, which has been extensively investigated (Bloxham et al., 1975 Eventoff et al., 1977). It catalyses the reversible oxidation of L-lactate to pyruvate using NAD+ as a coenzyme. The reaction scheme with a view of the active site with bound substrate and essential amino-acid side chains are depicted in Equation (3) and in Figure 17. The probable reaction mechanism, involving proton and hydride transfers,... 

It was discovered in 1958 that anaerobically grown yeast contains a form of lactate dehydrogenase which is different from the d- and L-lac-tate cytochrome c reductases of aerobic yeast (306, 319). The enzyme has been partially purified (320, 321), and shown to contain flavin (320-322). Gel filtration studies have suggested a molecular weight of about 100,000 (320, 321). Preparations of the enzyme oxidize several d-2-hydroxyacids to the respective keto acids in a reversible manner (320). For the forward reaction, ferricyanide, 2,6-dichloroindophenol, menadione, and methylene blue have been used as electron acceptors, and for the reverse reaction leucomethyl viologen and FMNHa are effective electron donors (320). A number of L-2-hydroxyacids and 2-keto acids have been shown to be competitive inhibitors. Oxalate, cyanide, o-phenanthro-line, and EDTA are also potent inhibitors (320, 321, 323, 324). The inhibition by metal chelators develops slowly and is reversed by addition of Zn, Co, Mn +, or Fe + (320, 323-326). Substrates prevent the inhibition by chelators at concentrations considerably lower than their respective Km values (327). It has been suggested that EDTA inactivation involves the removal of a metal, most probably Zn +, from the substrate binding site of the enzyme (325, 326, 328, 329). However, others have... 

Serum levels of lactate dehydrogenase (LDH) were formerly used to diagnose an acute Ml. LDH is present in cells as a tetramer of four identical, or nearly identical, subunits. Each subunit is a separate polypeptide chain with a molecular weight of 35 kD (approximately 35,000 g/mole). These subunits are present as two isoforms, the H isoform (for heart) and the M isoform (for skeletal muscle). Although the heart produces principally the H4 form (four H subunits combined into a tetramer) and skeletal muscles produce principally the M4 isoform, the heart, skeletal muscle, and other tissues produce several intermediate combinations (e.g., H3M, HjMj). These tetrameric isoforms all have similar activities, but the individual monomeric subunits are inactive. Measurements of LDH isozymes in the serum are no longer used for diagnosis of a recent Ml because the enzyme is large, released slowly, and the isozyme pattern is not as specific for the heart as is CK. 

Figure 1. Dependence of protein partition coefficient, Kp, on PEO molecular weight in a PEO-dextran-water two-phase system. In order of increasing size the proteins are (open circles) cytochrome-c, (filled circles) ovalbumin, (open diamonds) bovine serum albumin, (triangles up) lactate dehydrogenase, (triangles down) catalase, (open squares) pullulanase, (filled diamonds) phosphorylase. Data compiled from (26,27). The solid lines are drawn to guide the eye.

Isozymes are enzymes that catalyze the same biochemical reactions but differ based on molecular weight. For example, the electrophoretic mobility of lactate dehydrogenases (LDH), enzymes responsible for the... 

Anisotropy for the exploration of the mobility of domains of protein molecules is complemented with lifetime experiments briefly discussed in the next section. Another frequent use of static or time resolved steady state anisotropy measurements is the investigation of protein-protein and protein-nucleic acid interaction. An illustrative example is the association of dimeric to tetrameric lactate dehydrogenase from Bacillus stearothermo-philus labelled with fluorescamine (Clarke et al., 1985). In that case the rotational correlation time increases from 55 ns to 95 ns as the result of an increase in molecular weight from 80000 to 160000. 

Resolution of small molecular weight biomolecules Large scale HPAC application to rabbit muscle L-lactate dehydrogenase References... 

Lactate dehydrogenase Luteinizing hormone Luteotropic hormone Melanocyte-stimulating hormone Molecular weight... 

Certain enzymes exist in several different forms termed isoenzymes which are distinguishable by electrophoresis (mobility in an electric current) and by their immimochemistry. The different forms of the enzyme may occur in different tissues or alter in their relative proportions within the same tissue with time. The case which has been most studied is that of the five isoenzymes of lactate dehydrogenase which occur in mammalian tissues. Each isoenzyme has the same molecular weight (135,000) and is built up of foiu- polypeptide chains of two kinds (a and j8). The isoenzymes differ in their a, p make up thus 4a, 4j8, la + 3/S, 2a + 2/S, 3a - - 1/3. At least 33 different enzymes have been reported to exist as isoenzymes in plant tissues. 

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