Malate

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Malate

Description

Malic acid, C₄H₆O₅, occurs under physiological conditions as the anion malate^2-, M, with pK_a1 = 3.40 and pK_a2 = 5.20. L-Malate is formed from fumarate in the TCA cycle in the mitochondrial matrix, where it is the substrate of malate dehydrogenase oxidized to oxaloacetate. Malate is also formed in the cytosol. It cannot permeate through the lipid bilayer of membranes and hence requires a carrier (dicarboxylate carrier, tricarboxylate carrier and 2-oxoglutarate carrier). Malate alone cannot support respiration of mt-preparations from most tissues, since oxaloacetate accumulates in the absence of pyruvate or glutamate.

Abbreviation: M

Reference: Gnaiger 2014 MitoPathways

MitoPedia topics: Substrate and metabolite 

Application in HRFR

M: Malate (L-Malic acid, C₄H₆0₅); Sigma M 1000, 100 g, store at RT; FW = 134.1.

Preparation of 800 (or 400) mM stock solution (dissolved in H₂O):

1) Weigh 536.4 (or 268.2) mg of L-malic acid.

2) Add 3 ml H₂O.

3) Neutralize with 5 M KOH (approx. 350 µl).

4) Adjust final volume to 5 ml (in 5 ml volumetric glass flask).

5) Divide into 0.5 ml portions.

6) Store frozen at -20 °C.

Comment: 800 mM stock until 2013-11-20 (for 2 mM final concentration); 400 mM stock (for 0.5 mM final concentration) in discussion since then.

O2k manual titrations >> MiPNet09.12 O2k-Titrations

• Titration volume: 5 µl 800 mM (or 2.5 µl 400 mM) using a 25 µl Hamilton syringe (2 ml O2k-chamber).
• Final concenteration: 2.0 mM (or 0.5 mM).

Malate: 0.5 mM versus 2 mM in HRR

In mitochondrial preparations obtained from a diversity of tissues and organisms malate at concentrations >0.5 mM exerted an inhibitory effect on CII-linked and CI&II-linked respiration, whereas 0.5 mM malate was saturating for CI linked respiration. Selection of an optimum malate concentration for SUIT protocols is a compromise. Current investigations point towards 2 mM malate. Sumbalova_2016a_Abstract_MitoFit_Science_Camp_2016

• Further details: »Discussion.