Abstract: An assay with high sensitivity for activity of lecithin-cholesterol acyltransferase in blood for functional analysis of liver, by bringing the blood into contact with lecithin and free cholesterol until lysolecithin and cholesterol ester are produced, allowing the lysolecithin produced to react with lysophospholipase and glycerophosphocholine phosphodiesterase and assaying glycerol-3-phosphate produced simultaneously or successively in the reaction by means of an enzymatic cycling reaction in which glycerol-3-phosphate, dihydroxyacetone-3-phosphate, nicotinamide adenine dinucleotide (NAD), reduced NAD, O.sub.2, H.sub.2 O.sub.2, glycerophosphate oxidase and glycerophosphate dehydrogenase take part.

Abstract: A antibiotic L53-18A and a pharmaceutically acceptable salt thereof which are useful for treatment of bacterial inventions are obtained by culturing, for example, Saccharopolyspora sp. L53-18 (FERM BP 2231) in a medium and the antibiotic accumulated therein is collected.